CODEWITHSUNDEEP
c#winforms
LaCookie420
LaCookie420

Reputation: 11

Invoke or BeginInvoke cannot be called on a control until the window handler has been created

Within my program, I have two forms, formLogin and formStudent. The formLogin has a connection to a server, through an external class called Connection. I am attempting to pass the connection to formStudent, show the formStudent and hide the formLogin. The Connection class has two constructors for the forms so that I'm not creating new instances of the forms everywhere and it inherits Form.

The method I am attempting to call from the Connection class gives me the error shown in the comment:

public void SuccessfulLogin()
{
    if (this.InvokeRequired)
    {
        this.Invoke(new Action(() => SuccessfulLogin()));
        /*
        **Invoke or BeginInvoke cannot be called on a control until the window 
        handler has been created**
        */
    }
    else
    {
        formStudent.connection = formLogin.newConnection;
        formLogin.Hide();
        formStudent.Show();
    }
}

I have attempted adding if statements to see if the handle is created through if (IsHandleCreated), but through using break points it doesn't appear that any of the code in the method is being run at all. I have also tried placing this method in both the formLogin class and the Connection class, with no changes.

UPDATE:

Thank you very much to King King, for pointing me in the right direction. I changed my code to this:

this.CreateHandle();
this.Invoke(new MethodInvoker(SuccessfulLogin));

and the sucessfulLogin method to this:

public void SuccessfulLogin()
{
    if (this.InvokeRequired)
    {
        this.Invoke(new Action(() => SuccessfulLogin()));
    }
    else
    {
        formStudent = new frmStudent();
        formStudent.connection = formLogin.newConnection;
        formLogin.Hide();
        formStudent.Show();
    }
}

Upvotes: 1

Views: 771

Answers (1)

King King
King King

Reputation: 63317

Try using CreateControl() before calling to SuccessfulLogin():

 this.CreateControl();
 this.SuccessfulLogin();

Other solutions:

  • Call it in a Load event handler
  • Call it in a Shown event handler
  • Call it in a HandleCreated event handler (Of course, this should be done with some flag to make it work as expected, because the Handle may be re-created at runtime at some unpredicted point of time and hence may make the SuccessfulLogin called multitime).

Upvotes: 1

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