Question

I have a textbox in grid view created dynamically. We can access the user input as text, but how do I check whether the text is of integer type or string type?

if (tx.Text == "")
{
    tx.Text = Convert.ToString(0);
}
if (Convert.ToInt32(tx.Text) > max)
{
    MessageBox.Show("Some Message", "Error", MessageBoxButtons.OK, MessageBoxIcon.Information);
    tx.Text = Convert.ToString(max);
}

tx is the textbox from which we are accessing the user input through tx.Text.
How can I check the type of the input parameter whether it is Integer or not?

Answer 1

You’re looking for the TryParse method. That will tell you if a given string value can be converted into a number. And it does it all without throwing any exceptions.

Sample code:

  int number;
  bool result = Int32.TryParse(tx.Text, out number);
  if (result)
  {
      // Conversion to a number was successful.
      // The number variable contains your value.        
  }
  else
  {
     // Conversion to a number failed.
     // The value entered in the textbox is not numeric.
  }

But if you’re looking to restrict the input range of the textbox (i.e., prevent the user from entering anything but numbers), this is not the correct way to go about it.

Instead, you should use a different control, such as a NumericUpDown control, or a MaskedTextBox control. These allow you to prevent the user from entering invalid input in the first place, which is much more user friendly than showing an error after the fact.

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In response to your comment:

in java you have instanceof keyword to check for object type. eg:- Obj instanceof Integer …How do you check for the object type in C#

C# has the typeof keyword, but that’s not going to help you here. The problem is, the object you’re checking is an instance of type String. The Text property of the TextBox class always returns an object of type String. This is not VB 6: there are no Variants here. What you’re checking is whether that String value can be converted into an equivalent integral representation.