Question

I’ve a web page with a textbox as below –

<asp:TextBox ID="txtNumber" runat="server" size="5" MaxLength="9" 
    AutoPostBack="True" OnTextChanged="txtNumber_TextChanged" 
    CssClass="txtBoxPage" Style="margin-left: 3px;" 
    Visible="false" onblur="return [some JS function] false;">
</asp:TextBox>

I want a functionality such that if User enters Nothing i.e. (”) in textbox and move the cursor outside the textbox then Postback should not trigger. Currently it’s getting triggered even after onblur event returns false.

Answer 1

If textbox value is empty, you can supress TextChanged event as below –

• Remove onblur function and use onchange instead.

• Add following line in Page_Load –

  protected void Page_Load(object sender, EventArgs e)
  {
      txtNumber.Attributes.Add("onchange", "if(checkEmptyValue(this)) {return false; }");
  }
  

• Include following JavaScript in markup –

  String.prototype.trim = function() {     return this.replace(/^\s+|\s+$/g, ""); }; 
  
  function checkEmptyValue(o) {
      if (o.value == '' || o.value.trim() == '')
          return true;
      else
          return false;
  }
  

Try above code and let me know if it works.