FileUpload Control Validation

最新推荐文章于 2022-03-14 07:59:00 发布

lJean

最新推荐文章于 2022-03-14 07:59:00 发布

阅读量635

点赞数

分类专栏： ASP.NET 文章标签： validation extension file application server upload

ASP.NET 专栏收录该内容

75 篇文章

订阅专栏

本文介绍如何在ASP.NET中使用FileUpload控件实现客户端和服务端的文件类型验证，确保用户只能上传.xls或.xml文件，包括JavaScript客户端验证函数及C#服务端验证方法。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

http://www.beansoftware.com/ASP.NET-FAQ/FileUpload-Validation.aspx

With FileUpload control you can receive files from your web application users. Often, you don't want to receive all file types, but only specific extensions (e.g. images only) depending of your application requirements. Unfortunately, FileUpload control still have not some Filter property like Open and Save File dialogs in .NET Windows Forms to limit file types. Because of that, you need to write some additional code to be sure that user will upload regular file type.

Let say you have two web controls on web form, on FileUpload Control to select a file and one button control, like in image bellow:

Because in ASP.NET we have client and server side, validation could be done on client and on server. You need to have server side validation because of security reasons, but you also need client side validation because it is faster and more user friendly. Let see how to implement both types, for example our web application will allow only upload of .xls or .xml files.

1. ClientValidationFunction
<asp:FileUpload ID="fuData" runat="server" /> <asp:Button ID="btnUpload" runat="server" Text="Upload" /> <br /> <asp:CustomValidator ID="CustomValidator1" runat="server" ClientValidationFunction="ValidateFileUpload" ErrorMessage="Please select valid .xls or .xml file"></asp:CustomValidator> <mce:script language="javascript" type="text/javascript"></mce:script>

2. OnServerValidate

Because of security reasons, you need to validate FileUpload control on server side too. You can use the same idea like for client side validation. In this case, just use OnServerValidate event, like in code bellow:

[ C# ]
protected void CustomValidator1_ServerValidate(object source, ServerValidateEventArgs args) { // Get file name string UploadFileName = fuData.PostedFile.FileName; if(UploadFileName == "") { // There is no file selected args.IsValid = false; } else { string Extension = UploadFileName.Substring(UploadFileName.LastIndexOf('.') + 1).toLower(); if (Extension == "xls" || Extension == "xml") { args.IsValid = true; // Valid file type } else { args.IsValid = false; // Not valid file type } } }

[ VB.NET ]
Protected Sub CustomValidator1_ServerValidate(ByVal source As Object, ByVal args As System.Web.UI.WebControls.ServerValidateEventArgs) Handles CustomValidator1.ServerValidate ' Get file name Dim UploadFileName As String = fuData.PostedFile.FileName If UploadFileName = "" Then ' There is no file selected args.IsValid = False Else Dim Extension As String = UploadFileName.Substring(UploadFileName.LastIndexOf(".") + 1).ToLower() If Extension = "xls" Or Extension = "xml" Then args.IsValid = True ' Valid file type Else args.IsValid = False ' Not valid file type End If End If End Sub