Introduction

Here, we will see how to check the number of character has been inserted in the TextBox. A TextBox Which has max length 120 character and we insert a character in TextBox max length will be display 119 characters. When We enter 120 characters in the TextBox that will be the Max length.
Drag and drop a TextBox on the page. Select TextBox and press F4 to the property window.
  1. TextMode="MultiLine"
Now add the following code in the Head section of the .aspx page.
  1. <head runat="server">
  2. <title></title>
  3. <style type="text/css">
  4. .valid
  5. {
  6. background-color: #FFFFFF;
  7. color: #000000;
  8. }
  9. .invalid
  10. {
  11. background-color: #FFCCCC;
  12. color: #ff0000;
  13. }
  14. </style>
  15. <script language="javascript">
  16. function textCounter1(field, maxlimit)
  17. {
  18. if (field.value.length > maxlimit)
  19. {
  20. field.value = field.value.substring(0, maxlimit);
  21. document.getElementById('message').className = "invalid";
  22. document.getElementById('message').focus(); //alert('You have reached your maximum character limit.');}
  23. else
  24. {
  25. document.getElementById('message').className = "valid";
  26. }
  27. }
  29. function textCounter(field, countfield, maxlimit)
  30. {
  31. if (field.value.length > maxlimit) // if too long...trim it!
  32. field.value = field.value.substring(0, maxlimit);
  33. else
  34. countfield.value = maxlimit - field.value.length;
  35. }
  36. </script>
  37. </head>
Now add the following code in the body section.
  1. <body bgcolor="#FFFFFF">
  2. <form name="blah" action="" method="post" runat="server">
  4. <asp:TextBox ID="message" runat="server" name="message" onkeydown="textCounter(this.form.message,this.form.remLen,120)" onkeyup="textCounter1(this.form.message, 120)" class="validentry" Height="101px" TextMode="MultiLine" Width="228px"></asp:TextBox>
  5. <br/>
  6. <input readonly type="text" name="remLen" size="3" maxlength="3" value="120" position: absolute; style="width: 34px">Character left
  7. <br/>
  8. <br/>
  9. <br/>
  10. </form>
  11. </body>
Now run the application and check number of character has been inserted in the TextBox.
text1.gif
Figure1
Now Insert max length characters in TextBox.
text2.gif
Figure2