ASP.Net: Enable Disable TextBox based on another TextBox value using C# and VB.Net

Hi Ramco,

Please refer below sample.

HTML

<table>
    <tr>
        <td>Balance to be paid:</td>
        <td><asp:TextBox runat="server" ID="txtBalanceToBePaid" AutoPostBack="true" OnTextChanged="OnChanged" /></td>
    </tr>
    <tr>
        <td>Balance to paid:</td>
        <td><asp:TextBox runat="server" ID="txtBalanceToPaid" AutoPostBack="true" OnTextChanged="OnChanged" /></td>
    </tr>
    <tr>
        <td>Others:</td>
        <td><asp:TextBox runat="server" ID="txtOthers" /></td>
    </tr>
</table>

Code

C#

protected void OnChanged(object sender, EventArgs e)
{
    txtOthers.Enabled = true;
    int toPaid = int.Parse(!string.IsNullOrEmpty(txtBalanceToPaid.Text) ? txtBalanceToPaid.Text : "0");
    int toBePaid = int.Parse(!string.IsNullOrEmpty(txtBalanceToBePaid.Text) ? txtBalanceToBePaid.Text : "0");
    if (toPaid < toBePaid)
    {
        txtOthers.Text = string.Empty;
        txtOthers.Enabled = false;
    }
}

VB.Net

Protected Sub OnChanged(ByVal sender As Object, ByVal e As EventArgs)
    txtOthers.Enabled = True
    Dim toPaid As Integer = Integer.Parse(If(Not String.IsNullOrEmpty(txtBalanceToPaid.Text), txtBalanceToPaid.Text, "0"))
    Dim toBePaid As Integer = Integer.Parse(If(Not String.IsNullOrEmpty(txtBalanceToBePaid.Text), txtBalanceToBePaid.Text, "0"))

    If toPaid < toBePaid Then
        txtOthers.Text = String.Empty
        txtOthers.Enabled = False
    End If
End Sub

Screenshot