Disabling button after click - asp.net

Question

Private Function StoreCouponCode() As String
Dim con As New SqlConnection(ConfigurationManager.ConnectionStrings("DBConnectionString").ConnectionString)
Dim sql As New SqlCommand("", con)
Dim sqlGetSlNo As New SqlCommand("SELECT MAX(SlNo) FROM Coupons WHERE CustID=" & Convert.ToInt16(HFCustID.Value) & " AND BusiID=" & Convert.ToInt16(HFBusiID.Value) & " AND OfferID=" & Convert.ToInt16(HFOfferID.Value), con)
Dim sNo, UserID, couponCode, offerCheck As String
Dim slNo As Int16
Try
UserID = getCurrentUserID()
con.Open()
sNo = Convert.ToString(sqlGetSlNo.ExecuteScalar) 'fteches latest serial no for the coupon
If sNo = "" Then
slNo = 0
Else
slNo = Convert.ToInt16(sNo) + 1
End If
couponCode = MakeCouponCode(slNo)
offerCheck = couponCode.Substring(13, 3)
sql.CommandText = "INSERT INTO Coupons VALUES (" & _
HFCustID.Value & "," & HFBusiID.Value & "," & HFOfferID.Value & ",'" & _
Today.Date & "'," & Convert.ToString(slNo) & "," & offerCheck & ",'" & couponCode & "','" & _
UserID & "'," & LblPayInAdv.Text & "," & LblPayLater.Text & ",'" & Convert.ToString(Date.Now) & "')"
sql.ExecuteNonQuery()
con.Close()
Catch ex As Exception
couponCode = "N/A"
Finally
con.Dispose()
sql.Dispose()
End Try
Return couponCode
End Function
Protected Sub CmdGetCoupon_Click(ByVal sender As Object, ByVal e As System.Web.UI.ImageClickEventArgs) Handles CmdGetCoupon.Click
If User.Identity.Name = "" Then
LblMessage.Text = "You need to login first!"
Exit Sub
End If
Dim couponCode As String = StoreCouponCode()
Response.Redirect("~/Coupon.aspx?CouponCode=" & couponCode, True)
End Sub
When the user clicks on the CmdGetCoupon it takes some time to redirect..so the user clicks on the CmdGetCoupon more than once,which results in multiple coupon generation from a single user account.
I want to display a message "Please Wait While Your Coupon Is Being Generated" and disable the CmdGetCoupon so that the user cannot click multiple times....Any Ideas??How to do this??

Answer 1

Do this in javascript - use the OnClientClick to call a function that disables the passed in form element.
// On button
... OnClientClick="DisableMe(this);" ...
// Javascript
function DisableMe(elem)
{
elem.disabled = true;
// more code to show message
}

Answer 2

In your html side you have to add it in the onClientClick property:
<asp:Button ID="CmdGetCoupon" runat="server" onClientClick="this.disabled=true;" />
Edit:
Since #Oded so accurately pointed out that my first answer does not address the display of a message, here are a couple of options.
<span id="PleaseWaitContainer"></span>
<asp:Button ID="CmdGetCoupon" runat="server" onClientClick="this.disabled=true;document.getElementById('PleaseWaitContainer').innerText='Please Wait While Your Coupon Is Being Generated';" />
Or
<asp:Button ID="CmdGetCoupon" runat="server" onClientClick="this.disabled=true;alert('Please wait while your coupon is being generated...';" />

Answer 3

You can disable the button in the click handler, because you're going to redirect to another page, so don't care about any other logic.
Otherwise, if you're performing any async operation, again, disable it as soon as you click it, and in the async callback handler depending on the logic either enable it back or handle it properly in other way.