CODEWITHSUNDEEP
c#wpfwinformscombobox
user3012262
user3012262

Reputation: 67

How to disable read operation from Combobox in WinForms?

I know the command in WPF but what is its equivalent in WinForms?

cboclient.IsHitTestVisible = false;
cboclient.Focusable = false;

Using this command the combo-box is not disabled but the user can't open it for reading the data. How I can accomplish this in WinForms? thanks

Details: I have 3 combobox on my form when the form initially loads only the third combobox can not be opened for reading data. When the user selects a value in the first two combobox then based on those two values the third combobox is enabled to display data from DB.

Note: Here I don't want to disable the third combobox. Because it will give the user the a false expression.

Upvotes: 0

Views: 243

Answers (3)

Nitin Joshi
Nitin Joshi

Reputation: 1668

You can use following code:

cboclient.DropDownStyle = ComboBoxStyle.DropDownList;
cboclient.DropDownHeight = 1;
cboclient.DropDownWidth = 1;
cboclient.TabStop = false;

for displaying combobox as a readonly one you can use:

cboclient.FlatStyle = FlatStyle.Popup;

or

cboclient.FlatStyle = FlatStyle.Flat;

Upvotes: 0

King King
King King

Reputation: 63327

You can catch the message WM_MOUSEACTIVATE and discard it to prevent user from focusing the combobox by mouse and also prevent hittesting. Catch the message WM_SETFOCUS to prevent user from focusing the combobox by keyboard. Try this code:

public class ComboBoxEx : ComboBox
{    
    public ComboBoxEx(){
        IsHitTestVisible = true;
    }
    public bool IsHitTestVisible { get; set; }
    public bool ReadOnly { get; set; }
    protected override void WndProc(ref Message m)
    {            
        if (!IsHitTestVisible)
        {
            if (m.Msg == 0x21)//WM_MOUSEACTIVATE = 0x21
            {
                m.Result = (IntPtr)4;//no activation and discard mouse message
                return;
            }
            //WM_MOUSEMOVE = 0x200, WM_LBUTTONUP = 0x202
            if (m.Msg == 0x200 || m.Msg == 0x202) return;
        }
        //WM_SETFOCUS = 0x7
        if (ReadOnly && m.Msg == 0x7) return;
        base.WndProc(ref m);
    }
    //Discard key messages
    public override bool PreProcessMessage(ref Message msg)
    {
        if (ReadOnly) return true;
        return base.PreProcessMessage(ref msg);
    }
}
//Usage
comboBoxEx1.ReadOnly = true;
comboBoxEx1.IsHitTestVisible = false;

Upvotes: 1

J R B
J R B

Reputation: 2136

You can use if statement on OnSelectionChangedSelectionChanged event.

  private void ComboBox_SelectionChanged(object sender, SelectionChangedEventArgs e)
    {
      //here your if statement
    }

Upvotes: 0

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