Selecting a Row in ASPxGridView

I found that with the flood of new possibilities with DevExpress grid view a simple functionality of selecting one row is bit hidden. After doing bit of searching in the internet I found the way and thought to share it.

The way we need to do this is by using a java script and bind that in to the RowClick event of the grid.

The java script will look like the following.

<script type="text/javascript">
        function OnRowClick(e) {
            //Unselect all rows
            dxgdSearch._selectAllRowsOnPage(false);
            //Select the row
            dxgdSearch.SelectRow(e.visibleIndex, true);
        }
</script>

Then the binding to the RowClick would be as below.

<ClientSideEvents RowClick="function(s, e) { OnRowClick(e); }"></ClientSideEvents>

The outcome of this is a grid which you can select a row.

The value of the selected row can be taken as below.

dxgdSearch.GetRowValues(dxgdSearch.FocusedRowIndex, "Customer_ID")

For example in my application I used to pass the Customer Id to the Customer.aspx form as below.

 

 

1. Response.Redirect("~/Customer.aspx?cusID= " + dxgdSearch.GetRowValues(dxgdSearch.FocusedRowIndex, "Customer_ID"));
2. 
   

 

The full source is as of below.

Page.aspx

 

 

1. <asp:Content ID="Content4" ContentPlaceHolderID="MainContent" runat="server">
2.     <script type="text/javascript">
3.         function OnRowClick(e) {
4.             //Unselect all rows
5.             dxgdSearch._selectAllRowsOnPage(false);
6.             //Select the row
7.             dxgdSearch.SelectRow(e.visibleIndex, true);
8.         }
9.     </script>
10.     <dx:ASPxGridView ID="dxgdSearch" ClientInstanceName="dxgdSearch" runat="server" AutoGenerateColumns="False"
11.         SettingsBehavior-AllowFocusedRow="True" SettingsBehavior-AllowMultiSelection="False">
12.         <ClientSideEvents RowClick="function(s, e) { OnRowClick(e); }"></ClientSideEvents>
13.         <Columns>
14.             <dx:GridViewDataTextColumn Name="Id" ShowInCustomizationForm="True" VisibleIndex="1"
15.                 Caption="Customer ID" FieldName="Customer_ID" Visible="False">
16.             </dx:GridViewDataTextColumn>
17.             <dx:GridViewDataTextColumn Name="Name" ShowInCustomizationForm="True" VisibleIndex="0"
18.                 Caption="Name" FieldName="Full_Name">
19.             </dx:GridViewDataTextColumn>
20.             <dx:GridViewDataTextColumn Name="TelephoneNo" ShowInCustomizationForm="True" VisibleIndex="1"
21.                 Caption="Tele. No." FieldName="Mobile_Number">
22.             </dx:GridViewDataTextColumn>
23.             <dx:GridViewDataTextColumn Name="EMail" ShowInCustomizationForm="True" VisibleIndex="2"
24.                 Caption="EMail" FieldName="Email">
25.             </dx:GridViewDataTextColumn>
26.             <dx:GridViewDataHyperLinkColumn Name="Select" VisibleIndex="3">
27.                 <DataItemTemplate>
28.                     <asp:Button ID="Button1" runat="server" CommandArgument='<%# Eval("Customer_ID") %>'
29.                         OnClick="Button1_Click" Text="Edit" />
30.                 </DataItemTemplate>
31.             </dx:GridViewDataHyperLinkColumn>
32.         </Columns>
33.         <SettingsBehavior AllowFocusedRow="True"></SettingsBehavior>
34.         <Settings ShowGroupPanel="True" ShowFilterRow="True" />
35.         <Settings ShowFilterRow="True" ShowGroupPanel="True"></Settings>
36.     </dx:ASPxGridView>
37. </asp:Content>
38. 
    

Page.aspx.cs

 

 

1. protected void Button1_Click(object sender, EventArgs e)
2. {
3.     Response.Redirect("~/Customer.aspx?cusID= " + dxgdSearch.GetRowValues(dxgdSearch.FocusedRowIndex, "Customer_ID"));
4. }
5. 
   

Unable to start debugging on the web server

Recently a set of developers who are working in one of my projects started getting an error while trying to debug the web application under development using ASP.Net. The targeted framework was .Net 4.0 and they were using Visual Studio 2010 in 64bit machines. The problem was whenever they tried to run/debug the application they gets an error saying unable to start debugging on the web server even though there are no compile errors as shown below.

It gave an error HTTP Error 500.21 - Internal Server Error Handler "PageHandlerFactory-Integrated" has a bad module "ManagedPipelineHandler" in its module list when ran direct from IIS. The error page is shown below.

Later I found the reason for this is ASP.Net 4 was not properly installed on the machine. To fix this get an administrative privileged command prompt.

Then type in the following,

aspnet_regiis -ir

You can find the aspnet_regiis.exe at the folder,

[Windows Dir]\Microsoft.NET\Framework64\v4.0.xxxxx

for example,

C:\Windows\Microsoft.NET\Framework64\v4.0.30319

This will register ASP.Net 4.0 in your machine, the -ir option will keep the existing applications unchanged. If you want them to be changed to use the new version use -i instead -ir.

When the installer ends type iisreset to restart the IIS service.

Now your applications will work fine without any complains.

Connecting to MySQL in Visual Studio 2010

If you need to access MySQL databases using Visual Studio you have to install MySQL connector into your machine.

Currently only mysql-connector-net-6.3.1 is supporting Visual Studio 2010 which is still an alpha product.

To download it, use this link and switch to Development Releases tab.

Preserving State in ASP.Net

As you know a main challenge in web development is preserving the state of the application. We say web is stateless because web server treats each HTTP request for a page as an independent request. The server will not know any knowledge of variable values that were set/used during the previous requests. For example in Windows applications after we start the application if we set a variable to a certain value in a form it will be there until we close the form. But in web since the page is getting posted back the value will be normally lost.

To overcome this limitation in web ASP.Net provides two main methods and they are having different options under them.

1. Client Side State Management
   1. View State
   2. Cookies
   3. Query String
2. Server Side State Management
   1. Session State
   2. Application State
   3. Profile Properties

1.1- View State

Viewstate is a technique used in ASP.Net to preserve the state changes during the page postbacks. The viewstate data is always belong to the page, so this needs to be used when we want to store data at page level and retrieve them on the same page. Viewstate data will not be available from another page.

Viewstate uses a hidden form field named __VIEWSTATE as default to store the state information. When the “EnableViewstate” property of a control is set to true ASP.Net will start saving the control state in the viewstate. If we enable this property for many controls then soon the viewstate hidden variable will be large, and that may slow our application since this needs to be transferred at each postback. For example each time we submit a page the viewstate will go from our machine to server and from server to our machine. Due to this reason we should consider whether it is really required before enabling viewstate for a control. One advantage viewstate has is that it is not using server resources.

Apart from the viewstates of the controls in the form we can also add the values we need to preserve to the viewstate.

Adding a value -

1. ViewState["Text"] = value;

1. ViewState.Add("Text", value);

Retrieving a value -

1. object o = ViewState["Text"];

1. string str = (string) ViewState["Text"];

Read more at http://msdn.microsoft.com/en-us/library/bb386448.aspx.

1.2- Cookies

We use cookies to store frequently changed small amount of data at client side. We can control the life span of a cookie. For example we can create a cookie which expires when the session is over or which exists indefinitely in the client machine.

Cookies are light weight since they are text based structures having key value pairs. They are not taking any server resources since they are at client, but this also adds a disadvantage on security because users/hackers can tamper them. To prevent this we can encrypt cookies but this will reduce application performance. There is also a limit to the amount of data which we can be stored in a cookie. Also if cookies are blocked in browser the application will fail.

Adding a value -

1. Response.Cookies["userData"]["Name"] = "Arjuna";
2. Response.Cookies["userData"]["lastVisit"] = DateTime.Now.ToString();
3. Response.Cookies["userData"].Expires = DateTime.Now.AddDays(1);

1. HttpCookie aCookie = new HttpCookie("userData");
2. aCookie.Values["Name"] = "Arjuna";
3. aCookie.Values["lastVisit"] = DateTime.Now.ToString();
4. aCookie.Expires = DateTime.Now.AddDays(1);
5. Response.Cookies.Add(aCookie);

Retrieving a value -

1. HttpCookie cookie = Request.Cookies["userData"];
2. if (cookie == null)
3. {
4.     lblCookieText.Text = "Cookie not found.";
5. }
6. else
7. {
8.     lblCookieText.Text = cookie.Values[0] + ", " + cookie.Values["lastVisit"];
9. }

Read more at http://msdn.microsoft.com/en-us/library/ms178194.aspx.

1.3- Query String

A query string is the information added at the end of the URL. This is supported by all the browsers and does not consume server resources. But this has limited capacity and security problems.

Adding a value -

1. Response.Redirect("Webform2.aspx?Name=" +
2. this.txtName.Text + "&LastName=" +
3. this.txtLastName.Text);

Retrieving a value -

Using Webform2.

1. this.TextBox1.Text = Request.QueryString[0];
2. this.TextBox2.Text = Request.QueryString["LastName"];

 

2.1- Session State

Session state (variables) needs to be used to store session specific data. For example the logged in user information can be stored in session. Session variables are accessible by the entire set of pages in an application within the same session.

Session is created once a user visits a site and the session will end when the user leaves a site or when user becomes idle. Session variables are stored in a SessionStateItemCollection object that is exposed through the HttpContext.Session property. In an ASP.NET page, the current session variables are exposed through the Session property of the Page object. One disadvantage is that the session variables are taking server resources.

Adding a value -

1. Session["Name"] = “My Name”;

Retrieving a value -

1. string str = (string) Session["Name"];

Read more at http://msdn.microsoft.com/en-us/library/ms178581.aspx.

2.2- Application State

Application state (variables) are used to store application specific data. Application state will be accessible to any users connected to the application. Normally global data which are infrequently changed, having no security concerns are stored in an application state.

The HttpApplicatioState instance is created at the first time a user accesses any URL resource in an application and the application state is lost when the application is ended. For example if the web server is restarted. If the value is required after application restart then before application end the required values needs to be transfered to a non volatile medium such as a database for later retrieval. The HttpApplicationState class is most often accessed through the Application property of the HttpContext class. When using the application state we need to remove any unnecessary items as soon as it is not required to maintain the site performance.

Adding a value -

When adding a value to an application variable it is always good to lock it before adding data since application state data can be accessed by multiple threads at the same time. Otherwise invalid data or erroneous data will appear. The loack needs to be removed after adding or changing the value to make the application state available for other threads.

1. Application.Lock ();
2. Application["NumberofViews"] = 1;
3. Application.UnLock ();

Retrieving a value -

1. string str = (string)Application["NumberofViews"];

Read more at http://msdn.microsoft.com/en-us/library/ms178594.aspx.

2.3 Profile Properties

Profile properties uses an ASP.Net profile and is user specific. This is similar to session state except that the data stored in profile properties are not lost when session is ended.

We can store the profile data in a place that we like. If we are using SQL Server to store them then we can use SqlProfileProvider, if not we can write our own profile provider classes so the profile data will be stored in custom formats and in a custom storage mechanisms, such as an XML file, or even to a Web service. But performance will be less since the data is stored in a data store. Also to use it additional configurations and to keep it in a fully optimized level maintenance activities are required.

Adding a value -

First we need to add the required provider and the properties to the web.config file.

1. <profile enabled="true">
2.   <providers>
3.     <clear/>
4.     <add name="AspNetSqlProfileProvider" type="System.Web.Profile.SqlProfileProvider" connectionStringName="ApplicationServices" applicationName="/"/>
5.   </providers>
6.   <properties>
7.     <add name="UserName" />
8.   </properties>
9. </profile>

Retrieving a value -

1. TextBox1.Text = System.Web.Profile.DefaultProfile.Properties["UserName"].DefaultValue.ToString();

Read more at http://msdn.microsoft.com/en-us/library/2y3fs9xs.aspx.

Read more on ASP.Net state managements at http://msdn.microsoft.com/en-us/library/75x4ha6s.aspx.

"Login failed. The login is from an untrusted domain and cannot be used with Windows authentication."

If you are getting the above error while trying to connect to a database, the reason is you are using Windows Authentication to login to the SQL Server while being in another untrusted domain.

For example if the SQL Server machine is a member of the CompanyDomain and if you are in MyDomain or if you are in a Workgroup the you will face the above issue while trying to connect to the SQL Server.

The connection string used in the web.config while the above error is generated is as follows.

1. <connectionStrings>
2.   <add name="cnnStr" connectionString="Data Source=BI-SVR;Initial Catalog=BBIDatabase;Integrated Security=True"/>
3. </connectionStrings>

 

There are three ways to fix this problem.

1. Use the SQL Authentication to login to the SQL Server.

You can get this done by changing the connection string to use SQL authentication while connecting. But you need to know the credentials of an account which is having permissions to your required database or the System Administrator (SA) password. For simplicity I will use SA account details in the connection string.

1. <connectionStrings>
2.   <add name="cnnStr" providerName="System.Data.OleDb" connectionString="Data Source=BI-SVR;Persist Security Info=True;Password=YourPassword;User ID=sa;Initial Catalog=BBIDatabase"/>
3. </connectionStrings>

 

2. Login to your machine using the same Domain.

If you login to your machine using a domain account which the SQL Server is added to, then this error will vanish. But for this you need to add your machine to the same domain which the SQL Server machine is added to (CompanyDomain) also to properly get authenticated the account used should have proper permissions set to access the database in the SQL Server.

3. Make the account trusted in SQL Server.

By making the account you use to login to your machine trusted account in SQL Server and giving it appropriate permissions to access databases will also permit you to fix this error.

.Net Nullable Types

A variable of a nullable type can be used to store the normal range of values allowed by the underlying data type plus the Null. Nullable types are instances of System.Nullable.

Since reference types already supports Null, nullable types represent value type variables which supports null.

For example Nullable<bool> (or spoken like nullable of bool) can be used to store true, false and null.

There are two ways to declare a nullable variable.

Method 1

int? i; // Declaring
i = null; // Initializing

int? i = 4; // Declariong and initializing

Method 2

Nullable<int> a; // Declaring
a = 4; // Initializing

Nullable<int> a = null; // Declariong and initializing

As you see above assigning values to a nullable is same as for a normal variable. But when retrieving the value you need to be little careful.

Method 1 – Using GetValueOrDefault

GetValueOrDefault property is available for nullable variables. If the variable is null it will get the default value for the type otherwise the actual value it contains.

textBox1.Text += "Value of i - " + i.GetValueOrDefault();

Method 2 – Using variable.Value

When you are going to retrieve the value inside the variable using .Value be careful to first check whether there is actually a value in the variable, otherwise .Net will generate an InvalidOperationException with a description of “Nullable object must have a value”.

// \r\n is used to insert a new line.
if (i == null)
    textBox1.Text += "\r\n" + "i is Null";
else
    textBox1.Text += "\r\n" + "i is - " + i.Value;

or

// Environment.NewLine is equal to placing a new line or \r\n.
if (a.HasValue)
    textBox1.Text += Environment.NewLine + "a has - " + a.Value;
else
    textBox1.Text += Environment.NewLine + "a has Null";

The full code would look like the following.

1. // Declaring Method 1
2. int? i; // Declaring
3. i = null; // Initializing
4. //int? i = 4; // Declariong and initializing
6. // Get value using GetValueOrDefault().
7. textBox1.Text += "Value of i - " + i.GetValueOrDefault();
9. // \r\n is used to insert a new line.
10. if (i == null)
11.     textBox1.Text += "\r\n" + "i is Null";
12. else
13.     textBox1.Text += "\r\n" + "i is - " + i.Value;
15. // Declaring Method 2
16. //Nullable<int> a; // Declaring
17. //a = 4; // Initializing
18. Nullable<int> a = 4; // Declariong and initializing
20. // Environment.NewLine is equal to placing a new line or \r\n.
21. if (a.HasValue)
22.     textBox1.Text += Environment.NewLine + "a has - " + a.Value;
23. else
24.     textBox1.Text += Environment.NewLine + "a has Null";

The output would be,

Value of i - 0
i is Null
a has – 4

You could use the ?? operator to assign the default value for a non nullable variable while the nullable contains null as the current value.

int? Null_X = null;
int NonNull_y = Null_X ?? -1;

How to Read and Write Text

Reading and writing to text files had been made easy by .Net.

Following code will create a text file and insert 2 lines to it and will then read it and display.

1. // System.IO is required for file handling.
2. using System.IO;

1. // Creating a stream writer object.
2. // @ is used before the string to avoid the string getting broken by the /.
3. StreamWriter stWriter = new StreamWriter(@"C:\Backup\File.txt");
5. // Writing into the file.
6. stWriter.Write("It is now ");
7. stWriter.WriteLine(DateTime.Now);
8. stWriter.WriteLine("The End");
10. // Closing the file.
11. stWriter.Close();
13. // Reading the file.
14. // Checking the availability of the file.
15. if (File.Exists(@"C:\Backup\File.txt"))
16. {
17.     // Without using the @, \\ also can be used to represent \ inside of a string.
18.     using (StreamReader stReader = File.OpenText("C:\\Backup\\File.txt"))
19.     {
20.         // Temporary variable.
21.         string str = "";
22.         while ((str = stReader.ReadLine()) != null)
23.         {
24.             // Assigning to a label.
25.             label1.Text += str + "\n";
26.         }
27.     }
28. }
29. else
30.     MessageBox.Show("Error, File cannot be found.");

Reading and Writing to Excel Files

Even though I posted similar 2 articles in 2008, the code of that article was having few errors. So thought to put more complete post on this.

The code will read an Excel file using an OleDbConnection and will write the same data back to another Excel file. This will explain how to read and write to Excel files. One thing to remember when running this code is to make sure the source Excel file is open. Otherwise you will get an error similar to “External table is not in the expected format.”

Also note that there are few connection string parameters you can use while opening Excel files.

HDR = Yes – Use when first row contains column headers.

HDR = No  - Use when first row contains data.

Excel xx.x – Use the following Table as a guide.

Parameter Value	Excel Version
Excel 12.0	Excel 2007 (Released in 2007)
Excel 11.0	Excel 2003 (Released in 2003)
Excel 10.0	Excel XP (Released in 2001)
Excel 9.0	Excel 2000 (Released in 1999)
Excel 8.0	Excel 97 (Released in 1997)

 

IMEX=1 – Use this when you want to treat all your data in the file as text.

For example - >

Extended Properties="Excel 12.0 Xml;HDR=YES;IMEX=1";

To make the code to work properly you need to refer the Microsoft.Office.Interop.Excel assembly by adding a reference to your project.

1. using System;
2. using System.Data;
3. using System.Windows.Forms;
4. using System.Data.OleDb;
5. using Microsoft.Office.Interop.Excel;
7. namespace TestApp
8. {
9.     public partial class Form1 : Form
10.     {
11.         public Form1()
12.         {
13.             InitializeComponent();
14.         }
16.         private void button1_Click(object sender, EventArgs e)
17.         {
18.             openFileDialog1.ShowDialog();
19.             // Create an OLEDBConnection to connect to the Excel file.
20.             // I'm getting the required file by using a file dialog.
21.             // The @ symbol makes the string to contain any special characters inside the string without breaking the string.
22.             OleDbConnection dbConnection = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + openFileDialog1.FileName.ToString() + @";Extended Properties=""Excel 8.0;HDR=Yes;""");
23.             // Open the connection.
24.             dbConnection.Open();
25.             // Create a command object to work on the data.
26.             // Note that I have given the sheet name as [Sheet1$] to retrieve data from that named sheet in the particular Excel file.
27.             OleDbCommand dbCommand = new OleDbCommand("SELECT * FROM [Sheet1$]", dbConnection);
28.             // Creating a data reader to read data.
29.             OleDbDataReader dbReader = dbCommand.ExecuteReader();
30.             // If needed you can get the position of any column (e.g. Age), this will only work if you use HDR=Yes.
31.             int SearchingItem = dbReader.GetOrdinal("Age");
33.             // Create the Excel Application object.
34.             ApplicationClass ExcelApp = new ApplicationClass();
35.             // Set the visibility of the application.
36.             ExcelApp.Visible = true;
37.             // Create a new Excel Workbook.
38.             Workbook ExcelWorkbook = ExcelApp.Workbooks.Add(Type.Missing);
39.             // Create a new Excel Sheet.
40.             Worksheet ExcelSheet = (Worksheet)ExcelWorkbook.Sheets.Add(ExcelWorkbook.Sheets.get_Item(1), Type.Missing, 1, XlSheetType.xlWorksheet);
41.             // Will keep the current row index. This should start from 1 since the first row is 1.
42.             int CurrentRowIndex = 1;
43.             try
44.             {
45.                 // Read through the data.
46.                 while (dbReader.Read())
47.                 {
48.                     // Traverse through all the data columns.
49.                     for (int i = 0; i < dbReader.VisibleFieldCount; i++)
50.                     {
51.                         ExcelSheet.Cells[CurrentRowIndex, i + 1] = dbReader.GetValue(i);
52.                     }
53.                     CurrentRowIndex++;
54.                 }
55.                 // Save the Excel sheet.
56.                 // The @ symbol makes the string to contain any special characters inside the string without breaking the string.
57.                 ExcelApp.Save(@"C:\Projects\Ex.xls");
58.             }
59.             catch (Exception ex)
60.             {
61.                 MessageBox.Show(ex.ToString());
62.             }
63.         }
64.     }
65. }
66. 
    

Project has Stopped Working

If you create a .NET application to use SQL CE database when you try to run your application on a Windows Vista or Windows 7 machine you might get an error saying your application did stop working, and the error details might show that your are having a problem with System.Data.SQLServerCE.

The reason for this is that your system is not having the SQL Server CE runtime in your machine. To fix it what you need to do is to install the Microsoft SQL Server Compact 3.5 Service Pack 1 on your system. You can download it from the following Microsoft link.

http://www.microsoft.com/downloads/details.aspx?FamilyId=DC614AEE-7E1C-4881-9C32-3A6CE53384D9&displaylang=en

Disabling Date-Time Changes

Do you know that you can programmatically stop the user changing the date and time of a Pocket PC device?

This is useful if your applications need to take time accurately for some reason from the device.

The following code will disable the user from accessing the date time changing settings using his Windows Mobile powered device.

1. private void btnDisableClock_Click(object sender, EventArgs e)
2. {
3.     RegistryKey hklm = Registry.LocalMachine;
4.     hklm = hklm.OpenSubKey(@"\Software\Microsoft\Clock\", true);
6.     System.Byte[] offValue = new byte[1];
7.     offValue[0] = 0x30;
8.     hklm.SetValue("AppState", offValue);
10.     lblTitle.Text = "Change Clock Status - Disabled";
11. }

 

If you want to re-enable the setting, to make the user able to change the data and time use the below code.

1. private void btnEnableClock_Click(object sender, EventArgs e)
2. {
3.     RegistryKey hklm = Registry.LocalMachine;
4.     hklm = hklm.OpenSubKey(@"\Software\Microsoft\Clock\", true);
6.     System.Byte[] offValue = new byte[1];
7.     offValue[0] = 0x11;
8.     hklm.SetValue("AppState", offValue);
10.     lblTitle.Text = "Change Clock Status - Enabled";
11. }

Disabling Right Click

To disable right click context menu you can use one of the following methods.

Method 1 – Using attribute oncontextmenu attribute of the body tag.
By using this you can block the right click action and the context menu without using JavaScript.

1. <body oncontextmenu="return false">

This will be useless if you need to do some action on the click. In such a case use the Method 2.

 

Method 2 – Using JavaScript.

Place the following JavaScript and modify the script as you need. This will just show a popup window to the user saying that Right clicking is disabled.

1. <script language="javascript">
2.     document.onmousedown = disableRightClick;
3.     function disableRightClick(e) {
4.         if (event.button == 2) {
5.             alert("Right click is disabled.");
6.             return false;
7.         }
8.     }
9. </script>

Finding the Image Format

Here is a small code that I wrote to find the image format of an image.

This code will check for the raw image format of the image you select and will display in a pop up window.

Hope this helps.

1. using System.Drawing.Imaging;

1. private void button1_Click(object sender, EventArgs e)
2. {
3.     openFileDialog1.ShowDialog();
4.     Image img = Image.FromFile(openFileDialog1.FileName);
5.     ImageFormat imgfmt = img.RawFormat;
6.     if (imgfmt.Equals(ImageFormat.Bmp))
7.         MessageBox.Show(ImageFormat.Bmp.ToString());
8.     else if (imgfmt.Equals(ImageFormat.Jpeg))
9.         MessageBox.Show(ImageFormat.Jpeg.ToString());
10.     else if (imgfmt.Equals(ImageFormat.Tiff))
11.         MessageBox.Show(ImageFormat.Tiff.ToString());
12.     else if (imgfmt.Equals(ImageFormat.Wmf))
13.         MessageBox.Show(ImageFormat.Wmf.ToString());
14.     else if (imgfmt.Equals(ImageFormat.Icon))
15.         MessageBox.Show(ImageFormat.Icon.ToString());
16.     else if (imgfmt.Equals(ImageFormat.Png))
17.         MessageBox.Show(ImageFormat.Png.ToString());
18.     else if (imgfmt.Equals(ImageFormat.Gif))
19.         MessageBox.Show(ImageFormat.Gif.ToString());
20. }

Creating an Excel Sheet using .Net

In this entry I will show how you can create a Microsoft Excel file using .Net.

// Create the Excel Application object.
ApplicationClass ExcelApp = new ApplicationClass();
// Set the visibility of the application.
ExcelApp.Visible = true;
// Create a new Excel Workbook.
Workbook ExcelWorkbook = ExcelApp.Workbooks.Add(Type.Missing);
// Create a new Excel Sheet.
Worksheet ExcelSheet = (Worksheet)ExcelWorkbook.Sheets.Add(ExcelWorkbook.Sheets.get_Item(1), Type.Missing, 1, XlSheetType.xlWorksheet);
try
{
// Loop for 10 rows.
for (int rwCount = 1; rwCount <= 10; rwCount++)

{

// Loop for 3 columns.

for (int clmCount = 1; clmCount <= 3; clmCount++)

{

ExcelSheet.Cells[rwCount, clmCount] = "This is Row - " + rwCount + " Column - " + clmCount;

}

}

// Save the Excel sheet.

// The @ symbol makes the string to contain any special characters inside the string without breaking the string.

ExcelApp.Save(@"C:\Projects\Ex.xls");

}

Accessing Data in an Excel File using .Net

In this article I will show how you can open Microsoft Excel files using .Net.
You can use OLE objects to access data in Excel files as of you are accessing SQL Server data using SQL objects.

// Create an OLEDBConnection to connect to the Excel file.
// I'm getting the required file by using a file dialog.
// The @ symbol makes the string to contain any special characters inside the string without breaking the string.
OleDbConnection dbConnection = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + openFileDialog1.FileName.ToString()+ @";Extended Properties=""Excel 8.0;HDR=Yes;""");
// Open the connection.
dbConnection.Open();
// Create a command object to work on the data.
// Note that I have given the sheet name as [Sheet1$] to retrieve data from that named sheet in the particular Excel file.
OleDbCommand dbCommand = new OleDbCommand("SELECT * FROM [Sheet1$]", dbConnection);
// Creating a data reader to read data.
OleDbDataReader dbReader = dbCommand.ExecuteReader();
// Get the position of the column Desc 1.
int SearchingItem = dbReader.GetOrdinal("Desc 1");
// Read through the data.
while (dbReader.Read())
{
// Traverse through all the data columns.
for (int i = 0; i <>
{
ExcelSheet.Cells[CurrentRowCount, i + 1] = dbReader.GetValue(i).ToString();
}
}

Implementing a File Download in ASP.NET

Recently I gave some help to a colleague of mine implementing a file download. So I thought of sharing it with you.
If you need to make a web site user to download a file from your site you have to use HTTPResponse.Page.Response object. By using this you will be able to make the user download numerous kinds of files to their machines. The code required is as follows.

// This defines the type of the file that you are allowing to download.
Response.ContentType = "application/vnd.ms-excel";
// Path to the file to be downloaded.
string FilePath = MapPath("Xcel.xlsx");
// Initiating the file download.
Response.WriteFile(FilePath);
Response.End();

The above code will let the user download an Excel file named Xcel. Aprt from Excel you can use other file types as well by changin the Response.ContentType to the required file type.
A list of available content types are as follows.

Inserting a Double Quote in to a String in .NET

Even though this is not new I do forget this always, so thought of putting an entry on how we can put a double quote inside of a string.

VB.NET
Dim str As String = "Example String " & """" & "This is the String with double quotes." & """"
MessageBox.Show(str)

In VB.Net you can indicate that there is a double quote in a string by using 4 double quotes ("""").

C#.NET
string str = "Example String " + "\"" + "This is the String with double quotes." + "\"";
MessageBox.Show(str);

As you will notice in C# the double quote can be represented as double quote, back slash and again using two double quotes ("\"").

The above string will be displayed as follows.

Executing .NET Applications Located on a Remote Location

Have you tried executing an application which is on a remote machine from yours. Think it like this, you have an application written in .NET (any version) and two users are there who are willing to use the application using there machines. (Please note that in this secnario all the machines are in the same network.)

The normal process is to setup your application on both machines and tell them to use. But the problem is that you are not yet finished development so constatly there will be updates to the application. So if you install in two machines, all the time you change the application you have to install the new version in both machines. (This is ok as you think because it is only two machines, but think is there are 50 users using in 50 machines.)

In this kind of a scenario, installing the application in one machine and sharing it and making the other user access the same installation can ease your life. Isn't it?

If you just try running the application from the remote location, application might not work correctly. This is because you have to set a code group for the remote application in the local machine. Then only the local .NET classes will be accessible without problem to the remote application. To configure the things follow the points.

1. Install your required application in one machine and share the application folder if possible. (It doesn't really matter whether it is shared or not. What matters is the accessibility to the folder.) Run the application from the installed machine first to make sure the application is working properly in the local environment.

2. Install the required .NET framework on all the client (user) machines. (In my scenario above, in both uiser machines.) This is because the application is actually ran on the users machine even though it is located on a remote machine.

3. Browse to the application installation folder from a client (user) machine.
Get the 'Run' window by clicking on Start -> Run. Type the machine name or IP address of the machine where your application is installed (Note that my application resides in the machine having the IP 192.168.1.165 in my LAN).If the login criteria is asked, enter them and login. It is ok even if you use the 'Guest' account to log into the system if you have access to the shared application by the guest.
4. Open the .NET Configuration window by clicking on Start -> Control Panel -> Administrative Tools -> Microsoft .NET Framework x.x Configuration.

5. Expand the 'Runtime Security Policy' node from the left hand pane. Then expand the 'Enterprise' node and finally 'Code Groups' node. Then right click on 'All_Code' and click on New....

6. Specify a Name and Description for the code group and click Next.

7. Choose the condition type of the code group as 'URL'. In the underneath URL text box type the path to the remote application folder and put a backslash and an asterisk . In my case I typed file://192.168.1.165/Bin/* (The asterisk is used to include all the items under the folder Bin into the code group that we are creating). Then press Next.

8. From the list of existing permission sets select 'LocalIntranet' and click Next. Then click Finish in the next screen to finish and setup the new code group.

9. Now the code group is created for our remote application. But to make the application really run you have to change one property in the Code Group Properties. Continue by right clicking on the new code group that we created named 'My Code Group' and selecting 'Properties'. 10. In the code group properties, check the 'Policy levels below this level will not be evaluated' check box and press 'Ok' to apply the setting.

11. Close the open .NET Configuration windows and launch the application from the share.

If any specific functionality or if the entire application is not working please contact me, I might be able to help you out of the problem.