C# checking white space in a textbox

Question

How can I check in C# that is there a white space only in a textbox and perform some operation after that?

Answer 1

if (String.IsNullOrWhiteSpace(txtBox.Text))
{
    // so stuff
}

Answer 2

This ensures multiple spaces are caught in your check.

 bool hasAllWhitespace = txtBox1.Text.Length>0 &&
                         txtBox1.Text.Trim().Length==0;

To check for a single space only:

 bool hasSingleWhitespace = txtBox1.Text == " ";

Answer 3

        var Rxwhitesp = new Regex(@"\s");

        string textboxstring = textbox.Text;
        string textboxfirststring = textbox.Text.First().ToString();
        if (Rxwhitesp.IsMatch(textboxfirststring) && (textboxstring.Length == 1))
        {
            // write code for true condition
        }
        else
        {
            // write code for false condition
        }