access form from usercontrol

Question

I have a user control, that needs to access variables and static classes on Form1.cs. I can't find a working example on google. Any hints please? Thanks!

namespace WinApp1
{
public partial class Form1 : Form
{
    Public MyCustomClass myClass; // need to access this
    public Form1()
    {

    }
}
public static class Global {
   public static myGlobalVar; // Need to Access This
}
}

Abdusalam Ben Haj · Accepted Answer · 2013-02-17T13:41:20.780

8

Use this.Parent in UserControl to get the parent form :

Form1 myParent = (Form1)this.Parent;

then you can access the public field/property :

myParent.myClass

Note that if the UserControl is placed in a Panel inside the Form, you will need to get parent of parent.

You can access the static class by its name :

Global.myGlobalVar

edited Feb 17 '13 at 13:41

answered Feb 17 '13 at 13:12

Abdusalam Ben Haj

5,343
5
31
45

Thanks! I put the code in button click event inside my usercontrol, but I'm getting this reference error: The type or namespace name 'Form1' could not be found. Thanks! – Kristian Feb 17 '13 at 13:20
@Kristian Have you set different namespaces for Form1 and the usercontrol? – Abdusalam Ben Haj Feb 17 '13 at 13:21
the namespace is the name "WinApp1" for both form and user control. – Kristian Feb 17 '13 at 13:31
@Kristian That's strange, try `WinApp1.Form1` and see what happens – Abdusalam Ben Haj Feb 17 '13 at 13:33
My mistake, I renamed the form, I was able to access it using: WinForm1.frm1 myParent = this.Parent; but this gives me another error: Cannot implicitly convert type 'System.Windows.Forms.Control' to 'WinApp1.frm1'. An explicit conversion exists (are you missing a cast?) – Kristian Feb 17 '13 at 13:34
@Kristian Sorry forgot to cast, see my updated answer as an example – Abdusalam Ben Haj Feb 17 '13 at 13:35
Thanks that worked, but I can't still access my global class. It's defined as 'public static class Global'. Thanks! – Kristian Feb 17 '13 at 13:39
static classes dont have instances. You can access it with its classname. for example: MyClass.StaticMember – Boas Enkler Feb 17 '13 at 13:40
@Kristian You can access the global class by just calling the name and the method name straight, will update my answer – Abdusalam Ben Haj Feb 17 '13 at 13:40
oh, thank you very much for the help, everything worked out perfectly! – Kristian Feb 17 '13 at 13:49

Boas Enkler · Answer 2 · 2013-02-17T13:39:11.063

You can use FindForm()

But you should make a step back and see if this is the best solution. This is a strong dependency which reduces testability and reuse factor of your control.

For example consider introducing a interface with the members you need for your control and search it in the parent hirachy or Inject it as a parameter ,...

From there on you can use the control on my situations. There may be also many more solutions. Just want to make you think if there isn't anything better than relying on the form..

Ali.Rashidi · Answer 3 · 2013-07-01T19:04:45.573

Use :

frm_main frm;     //frm_main is your main form which user control is on it
frm=(frm_main)this.FindForm();     //It finds the parent form and sets it to the frm

now you have your main form. any change on frm will be reflected on the main form. if you want to access a specified control on your main form use:

1-Create a control of the type you want to access(Ex:Label):

Label lbl_main;

2-Set the label with returned control from search result:

frm.Controls.FindControl("controlId",true);

3-Make your changes on the Label:

lbl_main.Text="new value changed by user control";

Your changes will be reflected on the control. Hope that helps.

score 1 · Answer 4 · answered Feb 17 '13 at 13:20

1

I thought that this.Parent returns the actual page that the user control is placed? And then you access the public members

answered Feb 17 '13 at 13:20

d1mitar

226
2
13

score 1 · Answer 5 · answered Sep 11 '18 at 19:40

in your UserControl code, under Click event or whatever:

private void sendParamToMainForm_Button_Click(object sender, EventArgs e)
{
    mainForm wForm;
    wForm = (mainForm)this.FindForm();

    wForm.lblRetrieveText.text = "whatever ...";
}

Hope this helps :-)

score 0 · Answer 6 · answered Apr 06 '19 at 14:41

0

In case your user control is inside panels and you want to access the form
you can use

        Main_Form myform = (Main_Form)ParentForm;
        MessageBox.Show(myform.Label2.Text);

answered Apr 06 '19 at 14:41

Ashraf Eldawody

138
3
11

access form from usercontrol

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