1. function RestrictSpaceSpecial(e) {
  2. var k;
  3. document.all ? k = e.keyCode : k = e.which;
  4. return ((k > 64 && k < 91) || (k > 96 && k < 123) || k == 8 || k == 32 || (k >= 48 && k <= 57));
  5. }
Now access the JavaScript function on keypress event of textbox as shown below:
  1. <asp:TextBox ID="TextBox2" runat="server" onkeypress="RestrictSpaceSpecial();" />