Redirect based on confirm message box dialog selection in ASP.Net

Hi Vincenzo67,

Refer below sample.

HTML

<asp:Button ID="btnConfirm" runat="server" OnClick="OnConfirm" 
    Text="Raise Confirm" OnClientClick="Confirm()" />

JavaScript

<script type="text/javascript">
    function Confirm() {
        var confirm_value = document.createElement("INPUT");
        confirm_value.type = "hidden";
        confirm_value.name = "confirm_value";
        if (confirm("Do you want to save data?")) {
            confirm_value.value = "Yes";
        } else {
            confirm_value.value = "No";
        }
        document.forms[0].appendChild(confirm_value);
    }
</script>

Code

C#

public void OnConfirm(object sender, EventArgs e)
{
    string confirmValue = Request.Form["confirm_value"];
    switch (confirmValue)
    {
        case "Yes":
            this.Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('You clicked YES!')", true);
            break;
        case "No":
            this.Page.ClientScript.RegisterStartupScript(this.GetType(), "alert", "alert('You clicked NO!')", true);
            break;
        default:
            break;
    }
}

VB.Net

Protected Sub OnConfirm(sender As Object, e As EventArgs)
    Dim confirmValue As String = Request.Form("confirm_value")
    Select Case confirmValue
        Case "Yes"
            Me.Page.ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('You clicked YES!')", True)
        Case "No"
            Me.Page.ClientScript.RegisterStartupScript(Me.GetType(), "alert", "alert('You clicked NO!')", True)
        Case Else
    End Select
End Sub

Screenshot