How can I add Locked property to ComboBox?

[goodmorningsky]

Current ComboBox control doesn't have Locked Property as same as the Locked property in ComboBox in VB6.

Locked= false : prevent user changing text in combo box.

 

I tried to add this by inheriting ComboBox.

and overried OnKeyPress.

But, followings.. do work...

Please help..

 

bool locked=false;
public bool MyLocked{
 set{locked = value;}
}
protected override void OnKeyDown(KeyEventArgs e)
{
  if(locked)
  {
e.Handled=true;
  }
}

 

 

second try : this looks worked but, not..

It doesn't work when user type fast..

private string tempText;
	private bool byKeyStroke=false;
	protected override void OnKeyDown(KeyEventArgs e)
	{
		tempText = this.Text;
		byKeyStroke = true;
		if(textLocked)
		{
			e.Handled=true;
		}
	}
	protected override void OnTextChanged(EventArgs e)
	{
		if(textLocked && this.byKeyStroke)
		{				
			this.Text = tempText;
			byKeyStroke = false;
		}
	}
	

[Roey]

I use the DropDown and DropDownList properties for allowing clients to edit combobox data

[techmanbd]

set the dropdownstyle property to dropdownlist of the combobox

[goodmorningsky]

thanks..

But, those doesn't work as I need..

so, its there any ways doing it by handling event as I wrote previously.

[pendragon]

The first example works if you use the KeyPress event instead of the KeyDown event

[goodmorningsky]

Thank you for considering

Actually I tried with all 3 of Key events..

All don't work..

after

e.Handle = true;

still the OnTextChanged event called and text is modified.

 

e.Handle = true;

should prevent further event as I know..but, not..

[Roey]

Can I ask why setting the dropdown style doesn't work for you. I have lots of forms using that method, and found it worked OK.

[pendragon]

I ran a quick test to see if it was working on my machine and using the KeyPress worked, this is what I did

 

private void comboBox1_KeyPress(object sender, System.Windows.Forms.KeyPressEventArgs e)
{
if (this.comboBox1.Tag.ToString() == "LOCK")
{
	e.Handled = true;
}
}

 

I used the tag property as a quick way of testing.

 

This didn't allow me to type anything into the comboBox but it still allows you to select an item. If you don't want them to be able to select items then the easiest way to do this is by setting the enabled property to False, the only draw back is that it greys out the control.

[goodmorningsky]

Can I ask why setting the dropdown style doesn't work for you. I have lots of forms using that method, and found it worked OK.

 

Thank you for your comment.

 

the reason I don't want to use DropDownStyle is..

 

this.skyComboBox1.DropDownStyle=ComboBoxStyle.DropDownList;

this.skyComboBox1.Text = "Current Text"; //this is not shown

 

As shown above I can't set Text on Combobox.

 

I want some text to be shown on text area..

but, after chaing DropDownList style I can't set text..

[goodmorningsky]

Thank you pendragon.

You are absolutely right.

I'm sorry I missed referring that I'm inheriting ComboBox class.

 

I'm inheriting from ComboBox so that I can reuse it without handling event on every client. I can just set TextLocked property.

This make exactly SkyComboBox as same as ComboBox in VB6.

( I dont' use the name 'Locked' property since VS.NET use it for Form modification lock functionality.)

 

I don't know why this approach doesn't work, meaning if I use it inside of subclass.

 

Please check following class..

and feel free to comment about other methods..

public class DriverClass{
 private SkyComboBox skybox;
 ....
 public void NeedTextLocked(){
    skybox.TextLocked = true;
}
}

public class SkyComboBox:ComboBox{

 private bool textLocked;
 public bool TextLocked{
    set{ textLocked = value;}
    get{return textLocked;}
 }
 protected override void OnKeyPress(KeyPressEventArgs e)
 {
       if(textLocked)
       {
             e.Handled = true; //this doesn't work!!!!!!!!!!!!!!!
         }
  }

  //I created this since combo.SelectedItem = itemObject;
  //doesn't make the itemObject selected.
  public void SetSelectedItem(object item)
 {
     for(int i=0; i< this.Items.Count; i++)
     {
if(this.Items[i] == item){	
                   this.SelectedIndex = i;
               }
      }
  }

 //I created this since combo.SelectedText = "item Text"
 //doesn't make the item selected.
 public void SetSelectedText(string text)
 {
        text = text.Trim();
         for(int i=0; i< this.Items.Count; i++)
        {
Debug.WriteLine(this.Items[i].ToString());
if(this.Items[i].ToString().Equals(text))
   this.SelectedIndex = i;
         }
   }
}

Edited December 12, 2003 by goodmorningsky

[pendragon]

About the DropDownList, The only reason I know for it not setting the text is If it can't be found in the ComboBox's Item List.

 

As for you class this is the test I did

 

using System;
using System.Windows.Forms;

namespace MyComboBox
{

public class MyComboBox : ComboBox
{
	private bool isLocked;

	public bool IsLocked 
	{
		get 
		{
			return this.isLocked;
		}
		set 
		{
			this.isLocked = value;
		}
	}

	public MyComboBox()
	{

	}

	protected override void OnKeyPress(KeyPressEventArgs e)
	{
		base.OnKeyPress(e);
		if(this.isLocked == true)
		{
			e.Handled = true; 
		}
	}

}
}

 

This seems to be the same as yours but it works here, even with a button to toggle IsLocked (But as I said before it still lets me change the combobox by selecting an Item from the List). Have you done a messagebox to check the value of textLocked in the OnKeyPress event to make sure it is true, apart from that I don't know what to suggest :confused:

 

To select the Index, Item and text on the combobox I use the following

 

this.MyComboBox.SelectedIndex = this.MyComboBox.FindStringExact(text);

 

To make it so that they can't select an Item in the ComboBox I added the following to the class

 

 

private int iIndex = -1;

protected override void OnSelectedIndexChanged(EventArgs e)
{
base.OnSelectedIndexChanged(e);
if(this.isLocked == true)
{
	this.SelectedIndex = this.iIndex;
}
else 
{
	this.iIndex = this.SelectedIndex;
}
}

Edited December 13, 2003 by pendragon

[goodmorningsky]

Thanks..

Now I got it..

I forgot calling base method!!!

 

I often forget what I have to do certainly...when coding^^--> very bugging... I fill like Dolry..(watch finding nemo for this name)^^;;

[pendragon]

Glad to be of help and I know what you mean about forgetting things when coding i'm always doing it.:D