Calling a MDI Child's method from the MDI Parent in C#

Question

I have two forms. One is MDI parent and the other is the MDI child. When a button on the parent is clicked the form of the child opens. I have written a code to prevent the form from duplicating. Those methods are as;

public Form IsFormAlreadyOpen(Type FormType)
    {
        foreach (Form OpenForm in Application.OpenForms)
        {
            if (OpenForm.GetType() == FormType)
                return OpenForm;
        }
        return null;
    }

public static Form1 f1;
public void open_Form1()
    {
        Form UForm = null;
        UForm = IsFormAlreadyOpen(typeof(Form1));

        if (UForm == null)
        {
            UForm = new Form1();
            UForm.MdiParent = this;
            UForm.Show();
        }
    }

This piece of code is available in the MDI Parent form. and them the button is clicked the method "open_Form1()" is called and it open the child form.

But the problem is how can I access the public method which is written in the child form? On the child form i have this code.

    public void somefunction()
    {
        /*code*/
    }

How can i call this method from the MDI Parent?

Dai Dai · Accepted Answer · 2012-07-14T19:17:42

Once you've gotten a reference to a child form you need to cast it to the appropriate type then call the method. For example:

class MyChildForm : Form {}

Form childForm = GetAChildFormInstance();
MyChildForm castForm = (MyChildForm)childForm;
castForm.MyMemberMethod();

As a side note, you don't seem to have a naming convention. In .NET all public members (properties, fields and members) should be PascalCased. Locals (method variables and parameters) should be camelCase, and private fields can be _underscorePrefixed. Underscores should never be used in-between words in .NET.

Calling a MDI Child's method from the MDI Parent in C#

1 Answers