Calling a method in parent page from user control

问题:

I've a user control registered in an aspx page On click event of a button in the user control, how do i call a method which is there in the parent page's codebehind?

Thanks.

回答1:

Here is the classic example using events as suggested by Freddy Rios (C# from a web application project). This assumes that you want to use an existing delegate rather than make your own and you aren't passing anything specific to the parent page by event args.

In the user control's code-behind (adapt as necessary if not using code-behind or C#):

public partial class MyUserControl : System.Web.UI.UserControl
{
    public event EventHandler UserControlButtonClicked;

    private void OnUserControlButtonClick()
    {
        if (UserControlButtonClicked != null)
        {
            UserControlButtonClicked(this, EventArgs.Empty);
        }
    }

    protected void TheButton_Click(object sender, EventArgs e)
    {
        // .... do stuff then fire off the event
        OnUserControlButtonClick();
    }

    // .... other code for the user control beyond this point
}

In the page itself you subscribe to the event with something like this:

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        // hook up event handler for exposed user control event
        MyUserControl.UserControlButtonClicked += new  
                    EventHandler(MyUserControl_UserControlButtonClicked);
    }
    private void MyUserControl_UserControlButtonClicked(object sender, EventArgs e)
    {
        // ... do something when event is fired
    }

}

回答2:

Cast the page as the specific page in your project:

((MyPageName)this.Page).CustomMethod()

回答3:

I suggest you don't call the page method directly, as you would be tying your control to the specific page.

Instead expose an event, and have the page subscribe to it. It works for any number of pages, can more easily be used when the control is multiple times on a single page (perhaps even on a list) and is more in line with asp.control design.

回答4:

Scott Allen has a useful article on event bubbling from a user control to the parent page, which elaborates on the answer provided by Stephen M. Redd:

• Event Bubbling From Web User Controls in ASP.NET (C#)

回答5:

Follow good and appropriate approach,

Use event and delegate concept make delegate as same signature as your method in parent page and then assign parent methad to it in parent page load event then call this delegate through event in user control.

code sample and link is given below.

//Parent Page aspx.cs part

 public partial class getproductdetails : System.Web.UI.Page
 {
  protected void Page_Load(object sender, EventArgs e)
  {
   ucPrompt.checkIfExist += new uc_prompt.customHandler(MyParentMethod);
  }

  bool MyParentMethod(object sender)
  {
   //Do Work
  }
}

//User control parts
public partial class uc_prompt : System.Web.UI.UserControl
{
 protected void Page_Load(object sender, EventArgs e)
 {
 }

 public delegate bool customHandler(object sender);
 public event customHandler checkIfExist;
 protected void btnYes_Click(object sender, EventArgs e)
 {
  checkIfExist(sender);
 }
}

Read more details how it works (Reference) :-

Calling a method of parent page from user control

回答6:

I want to do this scenario:

• Call LoadEditCategory method (parent method).
• Parent method (LoadEditCategory) needs a int argument (CategoryID).
• Child user control is RightControlPanel that is in same parent page folder.

Child User control

1- Add a Action (_LoadEditCategory)

public Action<int> _LoadEditCategory = null;

<int> is int argument (CategoryID).

2- Use this Action in button event (btnSavebutton name) like this:

void btnSave_Click(object sender, EventArgs e)
{
    //123 is test integer for CategoryID
    _LoadEditCategory(123);        
}

Parent Page or parent user control

3- Add parent method

 private void LoadEditCategory(int CategoryID)
    {
     // CategoryID is 123 in my example
     //Do some things with CategoryID
    }

4- Add this code when load child user control (RightControlPanel)

//Load child user control
RightControlPanel si = this.LoadControl(this.ControlPath + "RightControlPanel.ascx") as RightControlPanel;
if (si != null) 
 {
   ...

   //For call parent method in child user control
   si._LoadEditCategory = c => LoadEditCategory(c);

   ...
 }

回答7:

 //c#
 //In parent page
 public void test(string S)
 {
    Label1.Text = S;
  }

 //In user control
 protected void Button1_Click(object sender, System.EventArgs e)
 {
 //Calling "test method" of parent page  from user control  
 ((object)this.Page).test("Hello!!");
 }

 'VB.Net 
'In parent page
 Sub test(ByVal S As String)
    Label1.Text = S
 End Sub

 'In user control
  Protected Sub Button1_Click(sender As Object, e As System.EventArgs) Handles Button1.Click
  'Calling "test method" of parent page  from user control  
  DirectCast(Me.Page, Object).test("Hello!!")
  End Sub 

回答8:

I love Stephen M. Redd's answer and had to convert it to VB. Sharing it here. Suggested edits welcome.

In the user control's code-behind:

Public Class MyUserControl
    Inherits System.Web.UI.UserControl

    'expose the event publicly
    Public Event UserControlButtonClicked As EventHandler 

    'a method to raise the publicly exposed event
    Private Sub OnUserControlButtonClick()

        RaiseEvent UserControlButtonClicked(Me, EventArgs.Empty)

    End Sub

    Protected Sub lbtnApplyChanges_Click(sender As Object, e As EventArgs) Handles lbtnApplyChanges.Click

        'add code to run here, then extend this code by firing off this event
        'so it will trigger the public event handler from the parent page, 
        'and the parent page can hanlde it

        OnUserControlButtonClick()

    End Sub

End Class

In the parent page subscribe to the event, so when the event is raised, your code will run here.

Public Class SalesRecord
    Inherits System.Web.UI.Page

    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        'hook up event handler for exposed user control event to handle this
        AddHandler MyUserControl.UserControlButtonClicked, AddressOf MyUserControl_UserControlButtonClicked

    End Sub

    ''' <summary>
    ''' code to run when user clicks 'lbtnApplyChanges' on the user control
    ''' </summary>

    Private Sub MyUserControl_UserControlButtonClicked()

        'this code will now fire when lbtnApplyChanges_Click executes

    End Sub

End Class

回答9:

You can use Session . Say when you click on a button in user control and when you want to call Parent page method then in event handler of button click set value as

Session["CallParent"]="someValue";

as button will post back the page . On Page_Load event of Parent Page add it

protected void Page_Load(object sender,EventArgs e)
{
   if(Session["CallParent"]!=null)
   {
      // here call the Parent Page method 
      Method1();
      // now make the session value null
     Session["CallParent"]=null;
    }
}

It is much more efficient