Enable disable button on text changed in c# winform

Question

I am developing an application, in which there is a button in search box (like one in itunes). I want to enable cancel button whenever there is text in text box and disable it when text box is empty. I tried with text_changed event on textbox with the following code, but it jump over the if condition. Even sender sends me correct values but i am unable to put it into if else.

private void textBox1_TextChanged(object sender, EventArgs e)
    {
        if (string.IsNullOrEmpty(sender.ToString()))
        {
            btn_cancel.Visible = false;
        }
        else
        {
            btn_cancel.Visible = true;
        }
    }

Please help

Inisheer · Accepted Answer · 2013-01-16 11:56:48Z

5

Here is a simple solution.

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        this.button1.Enabled = !string.IsNullOrWhiteSpace(this.textBox1.Text);
    }

Of course, you'll have to set the button.Enabled = false when the form initially loads since the textbox event won't fire on startup (true for all answers currently provided for your question).

edited Jan 16, 2013 at 11:56

answered Jan 16, 2013 at 3:49

Inisheer

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1 Comment

Inisheer Over a year ago

string.IsNullOrEmpty is another option depending on the .NET Framework version you are targeting. And obviously, either the Enabled or Visible property can be used here.

Tommaso Belluzzo · Accepted Answer · 2013-01-16 03:41:06Z

2

private void textBox1_TextChanged(object sender, EventArgs e)
{
    if (String.IsNullOrEmpty(textBox1.Text))
        btn_cancel.Visible = false;
    else
        btn_cancel.Visible = true;
}

answered Jan 16, 2013 at 3:41

Tommaso Belluzzo

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Comments

sa_ddam213 · Accepted Answer · 2013-01-16 03:40:24Z

1

Try this:

private void textBox1_TextChanged(object sender, EventArgs e)
{
    var textbox = sender as TextBox;
    if (string.IsNullOrEmpty(textbox.Text))
    {
        btn_cancel.Visible = false;
    }
    else
    {
        btn_cancel.Visible = true;
    }
}

sender.ToString() will always return System.Windows.Forms.TextBox you need to cast sender as TextBox and use the Text value for your null or empty check

answered Jan 16, 2013 at 3:40

sa_ddam213

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2 Comments

Simon Whitehead Over a year ago

This is unnecessary unless the OP is subscribing more than one textbox to the same event. If he isn't (which I assume), then he knows that sender is textBox1..

sa_ddam213 Over a year ago

I was just showing his mistake about sender.ToString() , I don't really care how he uses it.

Afshin · Accepted Answer · 2013-01-16 03:40:58Z

0

try casting the sender to TextBox :

if (string.IsNullOrEmpty(((TextBox)sender).Text))

answered Jan 16, 2013 at 3:40

Afshin

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2 Comments

Simon Whitehead Over a year ago

This is unnecessary unless the OP is subscribing more than one textbox to the same event. If he isn't (which I assume), then he knows that sender is textBox1..

Afshin Over a year ago

@SimonWhitehead I think you missed the point, we're trying to show his mistake, as sa_ddam213 well said...

Simon Whitehead · Accepted Answer · 2013-01-16 03:43:26Z

0

One liner:

btn_cancel.Visible = textBox1.Text.Length > 0;

answered Jan 16, 2013 at 3:43

Simon Whitehead

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Comments

Alex · Accepted Answer · 2013-03-18 13:07:13Z

0

This is how I'd do it:

private void textBox1_TextChanged(object sender, EventArgs e)
{        
    string text = ((sender as TextBox) == null ? string.Empty : (sender as TextBox).Text);
    this.button1.Enabled = (string.IsNullOrWhiteSpace(text) == false);
}

This doesn't assume the event source is a specific control and avoids an exception if by mistake it's attached to something that's not a TextBox.

answered Mar 18, 2013 at 13:07

Alex

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Comments

Shadow Egalitarian · Accepted Answer · 2023-09-06 14:52:16Z

0

private void textBox2_TextChanged(object sender, EventArgs e)
    { 
        if (textBox2.Text == "") 
        {
            button5.Enabled = false;
        }
        else
        {
            button5.Enabled = true;
        }
        
    }

answered Sep 6, 2023 at 14:52

Shadow Egalitarian

11 bronze badge

1 Comment

LordWilmore Over a year ago

Please add some description explaining what you believe was the problem, and why this solution fixes it.

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