devexpress-examples/aspxuploadcontrol-how-to-implement-a-custom-required-field-required-validation-e3908

Display an error icon if no file is selected.

Upload Control for ASP.NET Web Forms - How to implement custom validation rules

This example demonstrates how to display an error icon if no file is selected.

Overview

The main idea is to call the upload control's client-side GetText method to get the selected file's name. If no file is selected, the upload control displays an error icon.

function OnClick(s, e) {
    var isValid = uploadControl.GetText() != "";
    img.SetVisible(!isValid);
    if (isValid)
        uploadControl.Upload();
}

<dx:ASPxUploadControl ID="upload" runat="server" ClientInstanceName="uploadControl" ... />

<dx:ASPxImage ID="imgErrorIcon" runat="server" ClientInstanceName="img" ClientVisible="False" />

<dx:ASPxButton ID="btnCheck" runat="server" AutoPostBack="false" >
    <ClientSideEvents Click="OnClick" />
</dx:ASPxButton>

Files to Review

• Default.aspx (VB: Default.aspx)
• Default.aspx.cs (VB: Default.aspx.vb)

Documentation

• Upload Control