How to validate textbox only for spaces?

Question

I have a tex box in aspx page and i need to validate the text box. How can i do this at server side.

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

if(Textbox1.Text=="")
{
    lblError.Text ="Enter required field":
}

this is working when user leaves the text box blank. But when he enter white spaces the message is not shown. Is there any solution to this?

Answer 1

If your using .net 4.0 or above than following work.

if(string.IsNullOrWhiteSpace(Textbox1.Text))
{
      lblError.Text ="Enter required field";
}

otherwise you have to check manually...

int flag=0;
char[] c=Textbox1.Text.ToCharArray();
for(int i=0;i<c.length;i++)
{
    if(c[i]!=" ")
    {
       flag=1;
       break;
    }
}
if(flag==0 || Textbox1.Text==""|| Textbox1.Text==null)
      lblError.Text ="Enter required field";

this will check emptiness .null and whitespaces of TextBox