How to access public members and controls of master page in a child (content) page and Accessing Content page functions from a Master page

How to: Reference ASP.NET Master Page Content

You can write code in content pages that references properties, methods, and controls in the master page, with some restrictions. The rule for properties and methods is that you can reference them if they are declared as public members of the master page. This includes public properties and public methods. You can reference controls on the master page independently of referencing public members.

To reference a public member on the master page

1. Add a @ MasterType directive in the content page. In the directive, set the VirtualPath attribute to the location of the master page, as in this example:

   <%@ MasterType virtualpath="~/Masters/Master1.master" %>

   
   
   

   This directive causes the content page's Master property to be strongly typed.

   
   



2. 
   

   Write code that uses the master page's public member as a member of the Master property, as in this example, which assigns the value of a public property named CompanyName from the master page to a text box on the content page:

   
   
   

   Visual Basic

   
   
   

   CompanyName.Text = Master.CompanyName

   
   
   

   C#

   
   
   

   CompanyName.Text = Master.CompanyName;

   
   

To reference a control on the master page

• 
  

  Use the FindControl method, using the value returned by the Master property as the naming container.

  
  
  

  The following code example shows how to use the FindControl method to get a reference to two controls on the master page, a TextBox control and a Label control. Because the TextBox control is inside a ContentPlaceHolder control, you must first get a reference to the ContentPlaceHolder and then use its FindControl method to locate the TextBox control.

  
  
  

  Visual Basic

  
  
  

  Sub Page_Load()
      Dim mpContentPlaceHolder As ContentPlaceHolder
      Dim mpTextBox As TextBox
      mpContentPlaceHolder = _
          CType(Master.FindControl("ContentPlaceHolder1"), _
          ContentPlaceHolder)
      If Not mpContentPlaceHolder Is Nothing Then
          mpTextBox = CType(mpContentPlaceHolder. _
              FindControl("TextBox1"), TextBox)
          If Not mpTextBox Is Nothing Then
              mpTextBox.Text = "TextBox found!"
          End If
      End If
  
      ' Gets a reference to a Label control not in a 
      ' ContentPlaceHolder
      Dim mpLabel As Label
      mpLabel = CType(Master.FindControl("masterPageLabel"), Label)
      If Not mpLabel Is Nothing Then
          Label1.Text = "Master page label = " + mpLabel.Text
      End If
  End Sub

  
  
  

  C#

  
  
  

  void Page_Load()
  {
      // Gets a reference to a TextBox control inside 
      // a ContentPlaceHolder
      ContentPlaceHolder mpContentPlaceHolder;
      TextBox mpTextBox;
      mpContentPlaceHolder = 
        (ContentPlaceHolder)Master.FindControl("ContentPlaceHolder1");
      if(mpContentPlaceHolder != null)
      {
          mpTextBox = 
              (TextBox) mpContentPlaceHolder.FindControl("TextBox1");
          if(mpTextBox != null)
          {
              mpTextBox.Text = "TextBox found!";
          }
      }
      
      // Gets a reference to a Label control that not in 
      // a ContentPlaceHolder
      Label mpLabel = (Label) Master.FindControl("masterPageLabel");
      if(mpLabel != null)
      {
          Label1.Text = "Master page label = " + mpLabel.Text;
      }
  }

  
  

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Accessing Content page functions from a Master page

We can use VB’s CallByName function to call a function in the Content page. This will allow us to have, e.g., the validation function for a form stored within the form and thus have different validations for each form. Suppose we have functions in a Content page like:

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' function that receives a string and returns a string 
Public Function ValidateMe(ByVal strInput As String) As String 
    ValidateMe = "The input was: " + strInput 
End Function

' function that receives an Integer and returns an Integer 
Public Function SumMe(ByVal Input1 As Integer, _
       ByVal Input2 As Integer) As Integer 
    SumMe = Input1 + Input2 
End Function

Then, we can call them from the Master page by setting up wrapper functions that connect to the Content page object, and do the CallByName.

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Private Function CallContentPageStringFunction(ByVal FunctionName _
                 As String, ByVal aParamArray() As String) As String 
    Dim mpContentPlaceHolder As ContentPlaceHolder 
    mpContentPlaceHolder = _
      CType(FindControl("DetailsMaster_ContentPlaceHolder"), _
                        ContentPlaceHolder) 
    CallContentPageStringFunction = CallByName(mpContentPlaceHolder.Page, _
                                    FunctionName, vbMethod, aParamArray) 
End Function

Private Function CallContentPageIntegerFunction(ByVal FunctionName _
                 As String, ByVal aParamArray() As String) As Integer 
    Dim mpContentPlaceHolder As ContentPlaceHolder 
    mpContentPlaceHolder = _
          CType(FindControl("DetailsMaster_ContentPlaceHolder"), _
                            ContentPlaceHolder) 
    CallContentPageIntegerFunction = CallByName(mpContentPlaceHolder.Page, _
                                     FunctionName, vbMethod, aParamArray) 
End Function

Then, we can pass parameters and get the return value as shown here:

1. Using strings:
   

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   Dim aParams(0) As String 
   aParams(0) = "Stand Up and Fight" 
   Dim strReturnValue As String = _
     CallContentPageStringFunction("ValidateMe", aParams)

   
   
   

   The return value in this case will be "The input was: Stand Up and Fight".

   
   



2. Using integers:
   

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   ReDim aParams(1) 
   aParams(0) = 10 
   aParams(1) = 12 
   Dim intRet As Integer = _
       CInt(CallContentPageIntegerFunction("SumMe", aParams)) 

   
   
   

   The return value in this case will be 220.

   
   

References:

(MSDN) http://msdn.microsoft.com/en-us/library/xxwa0ff0(VS.90).aspx

(CodeProject) http://www.codeproject.com/KB/aspnet/Master_and_Contents.aspx