<script language="javascript" type="text/javascript"> function sumCalc() { var _txt1 = document.getElementById('<%= TextBox1.ClientID %>'); var _txt2 = document.getElementById('<%= TextBox2.ClientID %>'); var _txt3 = document.getElementById('<%= TextBox3.ClientID %>'); var _txt4 = document.getElementById('<%= TextBox4.ClientID %>'); var _txt5 = document.getElementById('<%= TextBox5.ClientID %>'); var t1 = 0, t2 = 0, t3 = 0, t4 = 0; if (txt1.value != "") t1 = txt1.value; if (txt2.value != "") t2 = txt2.value; if (txt3.value != "") t3 = txt3.value; if (txt4.value != "") t4 = txt4.value; _txt5.value = parseInt(t1) + parseInt(t2) + parseInt(t3) + parseInt(t4) ; } </script> <div><asp:TextBox ID="TextBox2" runat="servidor" Onchange="return sumCalc();"></asp:TextBox>
<div><asp:TextBox ID="TextBox3" runat="servidor" Onchange="return sumCalc();"></asp:TextBox>
<div><asp:TextBox ID="TextBox4" runat="servidor" Onchange="return sumCalc();"></asp:TextBox>
<div> Total:<asp:TextBox ID="TextBox5" runat="server" ></asp:TextBox></div>En código ASP.Net
<div> <asp:TextBox ID="TextBox1" runat="server" onchange="sumCalc()"></asp:TextBox> <asp:TextBox ID="TextBox2" runat="server" onchange="sumCalc()"></asp:TextBox> <asp:TextBox ID="TextBox3" runat="server" onchange="sumCalc()"></asp:TextBox> <asp:TextBox ID="TextBox4" runat="server" onchange="sumCalc()"></asp:TextBox> <asp:TextBox ID="TextBox5" runat="server"></asp:TextBox> </div>En Javascript
<script type="text/javascript"> function sumCalc() { var _txt1 = document.getElementById("TextBox1").value; var _txt2 = document.getElementById("TextBox2").value; var _txt3 = document.getElementById("TextBox3").value; var _txt4 = document.getElementById("TextBox4").value; if (_txt1 == "") _txt1 = 0; if (_txt2 == "") _txt2 = 0; if (_txt3 == "") _txt3 = 0; if (_txt4 == "") _txt4 = 0; var total = parseInt(_txt1) + parseInt(_txt2) + parseInt(_txt3) + parseInt(_txt4); if (!isNaN(total)) { document.getElementById('TextBox5').value = total; } } </script>