Accessing Form's Controls from another class

Question

I have a windows forms application with some controls added to the designer. When I want to change something (LIKE) enabling a text box from inside the Form1.cs, I simply use:

textBox1.Enabled = true;

but now I have a separated class called class1.cs.

How could I enable textBox1 from a static function class1.cs?

NOTE: I did not try any code because I am totally clueless about doing this.

Answer 1

EDIT: Lot of edit.

public partial class Form1 : Form
{
    // Static form. Null if no form created yet.
    private static Form1 form = null;

    private delegate void EnableDelegate(bool enable);

    public Form1()
    {
        InitializeComponent();
        form = this;
    }

    // Static method, call the non-static version if the form exist.
    public static void EnableStaticTextBox(bool enable)
    {
        if (form != null)
            form.EnableTextBox(enable);
    }

    private void EnableTextBox(bool enable)
    {
        // If this returns true, it means it was called from an external thread.
        if (InvokeRequired)
        {
            // Create a delegate of this method and let the form run it.
            this.Invoke(new EnableDelegate(EnableTextBox), new object[] { enable });
            return; // Important
        }

        // Set textBox
        textBox1.Enabled = enable;
    }
}

Answer 2

This is just another method:

TextBox t = Application.OpenForms["Form1"].Controls["textBox1"] as TextBox;

Answer 3

You can pass the instance of your Form to the class

 MyForm frm = new MyForm();

 MyClass c = new MyClass(frm);

Then your class can take that instance and access the textbox

 public class MyClass
 {

   public MyClass(MyForm f)
   {
      f.TextBox1.Enabled = false;
   }
 }

The design does not look OK

It is better to call the class in your form and based on the value returned, manipulate the textbox

//MyForm Class

 MyClass c = new MyClass();
 c.DoSomethings();
 if(c.getResult() == requiredValue)
   textBox1.enabled = true;
 else
   textBox1.enabled = false;

//MyForm Class ends here

UPDATE

public class Class1
{
   public static int SomeFunction()
   {
      int result = 1;
      return result;
   }

   public static void SomeFunction(out int result)
   {
      result = 1;
   }
}

Usage

if(Class1.SomeFunction() == 1)
   textBox1.Enabled = true;
else
   textBox1.Enabled = false;

OR

int result = 0;
Class1.SomeFunction(out result);

if(result == 1)
   textBox1.Enabled = true;
else
   textBox1.Enabled = false;

Answer 4

You could let your class1 have an event to enable the Textbox.

public class Class1
{
  public event Action<object, EventArgs> subscribe ;
  private void raiseEvent()
  {
     var handler = subscribe ;
     if(handler!=null)
     {
        handler(this,EventArgs.Empty);//Raise the enable event.
     }
  }
}

Let the class containing the TextBox subscribe to it somehow. In TextBox wrapper class

 public class TextBoxWrapper
       public void EnablePropertyNotification(object sender, EventArgs args) 
       {
          TextBox1.Enabled = true ; //Enables textbox when event is raised.
       }
       public TextBoxWrapper()
       {
         class1Instance.subscribe+=EnablePropertyNotification ;
       }

Answer 5

You shouldn't really change UI controls in your Form from your class1, but instead create a method or a property in class1 that would tell if the textbox should be enabled or not.

Example:

// I changed the name class1 to MySettings
public class MySettings
{
    public bool ShouldTextBoxBeEnabled()
    {
        // Do some logic here.
        return true;
    }

    // More generic
    public static bool SetTextBoxState(TextBox textBox)
    {
        // Do some logic here.
        textBox.Enabled = true;
    }

    // Or static property (method if you like)
    public static StaticShouldTextBoxBeEnabled { get { return true; } }
}

Then in your form:

MySettings settings = new MySettings();
textBox1.Enabled = settings.ShouldTextBoxBeEnabled();

// Or static way
textBox1.Enabled = MySettings.StaticShouldTextBoxBeEnabled;

// Or this way you can send in all textboxes you want to do the logic on.
MySettings.SetTextBoxState(textBox1);

Answer 6

To access/modify a Form Element property, just write this in your outside Class.

Form1.ActiveForm.Controls["textBox1"].Enabled = true;

Where textBox1 is the variable name of TextBox.

What this actually does: Gets the active Form object's control specified by the name in string.

WARNING: Active form means the form which is currently open and focused on. If you do something else on your computer, with your minimized WindowsForm application, the Form1.ActiveForm will not get the form, instead, it will give null, which can lead to errors later. Be careful!

Answer 7

In this example you have a form called Main.cs and a class called MyClass:

In MyClass (Note: the name of my Form Class = 'Main'):

Main ui = new Main();
ui.toolStripProgressBarStickers.PerformStep();

In (FormName).Designer.cs so in my case Main.designer.cs change the appropriate control from 'private' to 'public':

public System.Windows.Forms.ToolStripProgressBar toolStripProgressBarStickers;

This solved it for me. Thanks, Ensai Tankado

Answer 8

I had to do this at work and didn't find that any of these answers matched what I ended up doing, so I'm showing how I made it work.

First, initialize a copy of your class in your load event.

NameOfClass newNameofClass;

Then you want to bind to your class (in the load event):

textBox1.DataBindings.Add(new Binding("Enabled", newNameofClass, "textBox1Enabled"));

In your class, do the following:

private bool textBox1Enabled = false;
public bool TextBox1Enabled
{
    get
        {
            return textBox1Enabled;
        }
        set
        {
            textBox1Enabled = value;
        }
}

• The false setting will initialize your textbox to being disabled
• Set textBox1Enabled to true if you want to enable by default.
• If you have other logic to enable/disable the textbox, simply modify the value of textBox1Enabled accordingly.

Answer 9

based on the answer from @vr_driver you can do that to avoid problems with other containers like groupbox, panels...

TextBox t = Application.OpenForms["Form1"].Controls.Find("textBox1", true)[0] as TextBox;

Answer 10

Very easy:

Create an Instance of your Form Object where want to access the Elements from.

Form1 ui = new Form1();

and now change the Form Elements to "public" - like this in the Designer Code:

...
public System.Windows.Forms.TextBox textBox6;
...

Now you can access them like this in your Code:

ui.textBox6 ...

Answer 11

This is how you should do : I wrote the code below in my form class :

public static Form1 form = null;

    private delegate void SetImageDelegate(Image image);

    public Form1()
    {
        InitializeComponent();
        form = this;
    }

    public static void SetStaticImage(Image image)
    {
        if (form != null)
            form.pic1.Image = image;
    }

    private void setImage(Image img)
    {
        // If this returns true, it means it was called from an external thread.
        if (InvokeRequired)
        {
            // Create a delegate of this method and let the form run it.
            this.Invoke(new SetImageDelegate(setImage), new object[] { img });
            return; // Important
        }

        // Set textBox
        pic1.Image = img;
    }

and the code below should be in anouther class :

Form1 frm= Form1.form;
frm.pic1.Image = image;

Note that i changed private static Form1 form = null; to public static Form1 form = null;

Good Luck ... Written by Hassan Eskandari :)