CODEWITHSUNDEEP
c#textbox
orglce
orglce

Reputation: 543

Argument exception with Text Box

I have a text box. When I drag a file into it and click a button the file from text box is moved to another folder. But if I forget to drag a file to the text box and click a button, the program throws an Argument Exception that sourceFileName isnt't present.

private void button_Click(object sender, EventArgs e)
{
    // here occurs Argument Exception Because there isn't any TextBox.Text
    File.Copy(TextBox.Text, "C:/");

    if (String.IsNullOrEmpty(TextBox.Text))
        {
            MessageBox.Show("Please drag a file to the Tex Box!");
        }
}

How can I catch that Argument Exception of a missing Source File?

Upvotes: 0

Views: 286

Answers (6)

Kurubaran
Kurubaran

Reputation: 8902

 if (File.Exists(TextBox.Text.Trim()))
  {
    File.Copy(TextBox.Text, "C:/");
  }
else
  {
    MessageBox.Show("Please drag a file to the Tex Box!");
    return;
  }

Upvotes: 0

David
David

Reputation: 219057

But if I forget to drag a file to the text box

Then you need to do some error checking in your code. If it's possible in the UI to click the button without specifying a file, then your code can't assume that the file name will be present. (Currently it does.)

Try checking the condition before performing the file operations:

if (!string.IsNullOrEmpty(TextBox.Text))
    File.Copy(TextBox.Text, "C:/");

Maybe even take it a step further to check if the value actually is a valid file:

if (! string.IsNullOrEmpty(TextBox.Text))
    if (File.Exists(TextBox.Text))
        File.Copy(TextBox.Text, "C:/");

Add some else conditions to show appropriate messages to the user. Conversely, you can disable the button in the UI until the text box has a value. Or, well, you could take both approaches.

(As an aside, TextBox isn't a particularly good name for a variable. That's the name of an actual class, and probably the same class as the variable itself. It's best to differentiate between the class name and the variable instance name, especially if you're ever going to use static methods on that class.)

Upvotes: 2

Angus Connell
Angus Connell

Reputation: 419

I tend to use File.Exists to see if the file is there beforehand I like to use exceptions for exceptional cases, but that's personal preference

Upvotes: 1

Jonesopolis
Jonesopolis

Reputation: 25370

why do you do the check after? 

if (String.IsNullOrEmpty(TextBox.Text))
    MessageBox.Show("Please drag a file to the Tex Box!");
else
    File.Copy(TextBox.Text, "C:/");

you only want to perform the action if it's valid. Really you probably need a try/catch around the whole thing as multiple errors could happen

Upvotes: 1

gleng
gleng

Reputation: 6304

Move your String.IsNullOrEmpty statement before the other statement.

private void button_Click(object sender, EventArgs e)
{
    if (String.IsNullOrEmpty(TextBox.Text))
       MessageBox.Show("Please drag a file to the Tex Box!");
    else
       File.Copy(TextBox.Text, "C:/");  
}

Upvotes: 1

Habib
Habib

Reputation: 223402

Check for string.IsNullOrEmpty before File.Copy and if the TextBox is empty then return from the event. 

private void button_Click(object sender, EventArgs e)
{
    if (String.IsNullOrEmpty(TextBox.Text))
        {
            MessageBox.Show("Please drag a file to the Tex Box!");
            return; // return from the event
        }

    File.Copy(TextBox.Text, "C:/");
}

Also its better if you use string.IsNullOrWhiteSpace, since it will check for null, string.Empty and white spaces (Only if you are using .Net framework 4.0 or higher)

Upvotes: 3

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