The File Upload server control provided by ASP.NET allows users to upload one or more files to the server. By default, ASP.NET permits only files that are 4,096 KB (or 4 MB) or less to be uploaded to the Web server. To upload larger files, you must change the maxRequestLength parameter of the <httpRuntime> section in the Web.config file.

<system.web>
  <httpRuntime executionTimeout="240" maxRequestLength="20480" />
</system.web>  

 The value of maxrequestlength is in KB. In this case it's allowed up to 20 MB

Here is sample code for TextBox Validation to allow Numbers only.

[code:c#]

[/code]

In Code behind add this function to "onkeyup" event for TextBox

[code:c#]

TextBox1.Attributes.Add("onkeypress", "CheckTextBox(this)");

[/code]

Some times we need to auto-refresh page after few seconds. you can do it with Meta Refresh tags

Where content '180' is the number of seconds.

Another approach is by addding HTTP header..

[code:c#]

[/code]

Here is sample code for adding tooltip to DropDownList. The key here is adding "title" attribute to the list items in DataBound event.

<asp:DropDownList ID="DropDownList1" runat="server" ondatabound="DropDownList1_DataBound">
</asp:DropDownList>

protected void DropDownList1_DataBound(object sender, EventArgs e)
{
    DropDownList ddl = sender as DropDownList;
    if (ddl != null)
    {
        foreach (ListItem li in ddl.Items)
        {
           li.Attributes["title"] = li.Text; // setting text value of item as tooltip

        }
    }

}

 
<script type="text/javascript" language="javascript">
function CustomValidator1_ClientValidate(source,args)
{ 
var listbox = document.getElementById("<%=ListBox1.ClientID %>");
var total = 0;
var i=0;
for( i = 0; i < listbox.options.length; i++ )
{
 if (listbox.options[i].selected) 
  {
   total ++; 
    if (total >10) {
      args.IsValid = false;
      return;
  }
  } 
 } 
 args.IsValid = true; return;
}
</script>
 
<asp:ListBox ID="ListBox1" runat="server" SelectionMode="Multiple" Height="100%"
Width="100%"></asp:ListBox>
<asp:Button ID="Button3" runat="server" OnClick="Button1_Click" Text="Button" />
<asp:CustomValidator ID="CustomValidator1" runat="server" Display="Dynamic" ErrorMessage="Please select 10 items only."
ClientValidationFunction="CustomValidator1_ClientValidate" OnServerValidate="CustomValidator1_ServerValidate">
</asp:CustomValidator>

Code Behind:

protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args) 
{ 
  int count = 0; 
  for (int i = 0; i < ListBox1.Items.Count; i++) 
  { 
        if (ListBox1.Items[i].Selected) 
            count++; 
  } 
 args.IsValid = (count > 10) ? false : true; 
} 

In Asp.Net ListBox, there are no events for Click action. The follwing code is useful in this regard..

[code:c#]

protected void Page_Load(object sender, EventArgs e)

{

if (Request["__EVENTARGUMENT"] != null && Request["__EVENTARGUMENT"] == "submit")    {       

//your code for click action

                                                      }

ListBoxNames.Attributes.Add("ondblclick", ClientScript.GetPostBackEventReference(ListBoxNames, "submit"));

}

[/code]

Some times we need to call server side function from Javascript function.For example,callig a PoupWindow(with value from code behind) on HyperLink click. 

This must be implemented by creating a additional request to the web server and that’s the only way to invoke methods on the server. Page methods are used for this.

What is PageMethod?

A PageMethod is a public static method that is exposed in the code-behind of a page and can be called from the client script. PageMethods are annotated with [System.Web.Services.WebMethod] attribute.

The code is simple..

Server side function

[code:c#]

[System.Web.Services.WebMethod] public static void Score(string ID, string name, string Role) {

         try {

                //Some data manipulations 

                  return finalScore ; 

              }

         catch (Exception ex) { 

               //Response.Write(ex.ToString());

                                  } 

            } 

[/code]

//Client Side function 

[code:c#]

function score()

              {               

                  PageMethods.Score(txtID.value,txtName.value,txtRole.value);            

               } 

[/code]

<asp:HyperLink ID="btn_Test" runat="server" Text="Calculate" OnClientClick="javascript:return score();"/> 

The ListSearchExtender lets you search for items in a ListBox or DropDownList by typing.  The extender performs an incremental search within the ListBox based on what has been typed so far.

the code is simple 

 <ajaxToolkit:ToolkitScriptManager ID="ScriptManager1" EnablePartialRendering="true" EnableScriptGlobalization="true" EnableScriptLocalization="true" runat="Server" />

ScriptManger is required for all AJAX controls..

 <ajaxToolkit:ListSearchExtender ID="ListSearchExtender1" runat="server" TargetControlID="ListBox1" PromptCssClass="ListSearchExtenderPrompt" PromptPosition="Top"></ajaxToolkit:ListSearchExtender/>

• PromptText - Message to display when the ListBox is given focus. 
• TargetControlID - Control to be searched
• PromptPosition - Indicates whether the message should appear at the Top or Bottom of the ListBox.  The default is Top.

For a Textbox with Read-only property set to true, text is not be posted back to the server side.

From MSDN..

The Text value of a TextBox control with the ReadOnly property set to true is sent to the server when a postback occurs, but the server does no processing for a read-only text box. This prevents a malicious user from changing a Text value that is read-only.

To set a Textbox read-only and keep the text on post back, use the following code..

We can get it from the Request object as shown below…

  TextBox1.Text = Request[TextBox1.UniqueID]; //Another approach… 

  TextBox1.Text = Request.Form[TextBox1.ClientID.Replace("_", "$")];