Loading WebUserControls `.ascx` files at runtime gives you the ability to create a dynamic page, the ability to create a page that accept plugins.

The problem is when you load WebUserControl at runtime, any postback caused by the page or the control itself will cause the control to disappear, here is a simple way explaining how to load these controls and maintaining them after postback.

First create two WebUserControls as shown below:

In the Save Button's code behind for both controls, write the following code:

          
            

            
          
          protected
          
          
          void
           butSave_Click(
          object
           sender, 
          EventArgs
           e)

{

   Label1.Text = TextBox1.Text;

}

        

Then create an `aspx` page with three Buttons and a Panel on the page as shown below:

Write the following code in page's code behind:

          
            

            
          
          protected
          
          
          void
           Page_Load(
          object
           sender, 
          EventArgs
           e)

{

             if
           (ViewState[
          "myControl"
          ]
!= 
          null
           && ((
          string
          )ViewState[
          "myControl"
          ])
!= 
          string
          .Empty)

   {

                UserControl
           uc
= LoadControl(ViewState[
          "myControl"
          ]
+ 
          ".ascx"
          ) 
          as
          
          
          UserControl
          ;

      uc.ID = ((

          string
          )ViewState[
          "myControl"
          ]);

                // Do
not clear Panel1's controls in `Page_Load` using `Panel1.Controls.Clear()`
          

                  // in some cases
the control's viewstate will be lost.

          
          
            

      Panel1.Controls.Add(uc);

            

   }

            

}

            

 

            

            
          
          protected
          
          
          void
           butLoadControl1_Click(
          object
           sender, 
          EventArgs
           e)

{

   ViewState[

          "myControl"
          ] = 
          "WebUserControl1"
          ;

             UserControl
           uc
= LoadControl(
          "WebUserControl1.ascx"
          ) 
          as
          
          
          UserControl
          ;

   uc.ID = 

          "WebUserControl1"
          ;

   Panel1.Controls.Clear();

   Panel1.Controls.Add(uc);

}

 

          protected
          
          
          void
           butLoadControl2_Click(
          object
           sender, 
          EventArgs
           e)

{

   ViewState[

          "myControl"
          ] = 
          "WebUserControl2"
          ;

             UserControl
           uc
= LoadControl(
          "WebUserControl2.ascx"
          ) 
          as
          
          
          UserControl
          ;

   uc.ID = 

          "WebUserControl2"
          ;

   Panel1.Controls.Clear();

   Panel1.Controls.Add(uc);

}

 

 

        

Run the code, and test it your self.

To download a sample project click the below link:

I just found a few minutes ago, that you can take an ASP.NET 2.0 application offline temporarily by uploading a file called App_Offline.htm.  It will spin down the appdomain and redirect all requests to that page.

I found a great post on dmitryr's blog on how to find the current trust level for your ASP.NET application, it is practical if you are hosting your site on a hosting company as the hosting company can set the trust level for your application in their machine.config file, and set it un-overridable.

Here is how to check the trust level:

Create an aspx page and place a Label:

In code behind...

Run the page and it will tell you what trust level your application has.

I use a website provided by the mobile phone company to send SMS messages, and charge it to my mobile phone, good to send bulk messages to friends and family.

I thought about using an automated method to send SMS to make it easier, I asked the mobile phone company if they provide something like a WebAPI or SMPP, but they don't.

So... I thought about using their form, and here come the greate HttpWebRequest and HttpWebResponse.

First I opened the login page... opened the page source, search for all form fields, login id, password and hidden fields.

Then I opened the Send SMS page... and did the same.

Now writing a test page:

It is working :D as expected.

Source: http://blah.winsmarts.com/2006/05/20/loadcontrol-a-usercontrol--and-pass-in-constructor-parameters.aspx

The inability of LoadControl to accept Constructor Parameters is a real pain in the donkey. This post tells you how to get around that hella annoying issue.

The awesome thing about ServerControls in ASP.NET is that you can instantiate them via a constructor, and hence offer a programming model similar to windows forms user controls. Unfortunately, you can't apply the same concept to UserControls because they are really mini pages within themselves. So you are limited to calling something like -

LoadControl("WebUserControl.ascx") ;

Wouldn't it be nice if you could instead do ...

LoadControl("WebUserControl.ascx",constructorparameter1, constructorparameter2, constructorparameter3 ...) ;

So say for instance, it would be nice if the following code would work -

Control toAdd = LoadControl( "WebUserControl.ascx" , "Sahil Malik" ,5) ;
PlaceHolder1.Controls.Add(toAdd) ;

Note: There is a new overload new in .NET 2.0 which takes the signature LoadControl(Type,object[]), which is very similar to the above. But it is frequently problematic in ASP.NET 2.0 to refer to a user control in a strongly typed manner.

Well, here is how you'd make it work.

1. First of all write the user control (Duhh!!). My user control has a label on it called Label1, and it has the following code-behind.

public partial class WebUserControl : System.Web.UI.UserControl
{
    public WebUserControl()
    {
    }

    public WebUserControl(string labelText, int howManyTimes)
    {
        System.Text.StringBuilder sb = new System.Text.StringBuilder() ;
        for (int i = 1; i <= howManyTimes; i++)
        {
            sb.Append(labelText) ;
            sb.Append("<br>") ;
        }
        Label1.Text = sb.ToString() ;
    }
}

As you can see, I am simply appending the same text over and over again. Note that it is important to explicitly create a default public constructor (i.e. one without parameters) or you'd confuse the ASP.NET runtime.

2. Step #2 is to add the following private method to your default.aspx, or add it as a protected method to the base class of all your pages, or a static method that can somehow access your page object. In my case I kept things simple and added a private method to my default.aspx.

private UserControl LoadControl(string UserControlPath, params object[] constructorParameters)
{       
    List<Type> constParamTypes = new List<Type>() ;
    foreach (object constParam in constructorParameters)
    {
        constParamTypes.Add(constParam.GetType()) ;
    }

    UserControl ctl = Page.LoadControl(UserControlPath) as UserControl;

    // Find the relevant constructor
    ConstructorInfo constructor = ctl.GetType().BaseType.GetConstructor(constParamTypes.ToArray()) ;

    //And then call the relevant constructor
    if (constructor == null)
    {
        throw new MemberAccessException("The requested constructor was not found on : " + ctl.GetType().BaseType.ToString()) ;
    }
    else
    {
        constructor.Invoke(ctl,constructorParameters) ;
    }

    // Finally return the fully initialized UC
    return ctl;
}

3. And finally, add the following to the Page_Load (or any other suitable place) of your default.aspx -

protected void Page_Load(object sender, EventArgs e)
{
    Control toAdd = LoadControl("WebUserControl.ascx","Sahil Malik",5) ;
    PlaceHolder1.Controls.Add(toAdd) ;
}