Replace special characters before saving file with Regular Expressions in ASP.Net using C# and VB.Net

Hi georgeacuster...,

You need to first find filename without extension using GetFileNameWithoutExtension method.

After that find file extension using GetExtension method.

Then use RegularExpression to replace special character Regex.Replace and add the extension.

Please refer below sample.

HTML 

<asp:FileUpload ID="fuDetails" runat="server" />
<asp:Button Text="Upload" OnClick="Upload" runat="server" />
<br />
<asp:Label ID="lblFileName" runat="server" />

Namespaces

C#

using System.IO;
using System.Text.RegularExpressions;

VB.Net

Imports System.IO
Imports System.Text.RegularExpressions

Code

C#

protected void Upload(object sender, EventArgs e)
{
    string fileNameWithoutExtension = Path.GetFileNameWithoutExtension(fuDetails.PostedFile.FileName);
    string fileExtension = Path.GetExtension(fuDetails.PostedFile.FileName);
    string fileNameCheckName = Regex.Replace(fileNameWithoutExtension.ToUpper(), @"[^\w]", "_") + fileExtension;
    lblFileName.Text = fileNameCheckName;
}

VB.Net

Protected Sub Upload(ByVal sender As Object, ByVal e As EventArgs)
    Dim fileNameWithoutExtension As String = Path.GetFileNameWithoutExtension(fuDetails.PostedFile.FileName)
    Dim fileExtension As String = Path.GetExtension(fuDetails.PostedFile.FileName)
    Dim fileNameCheckName As String = Regex.Replace(fileNameWithoutExtension.ToUpper(), "[^\w]", "_") & fileExtension
    lblFileName.Text = fileNameCheckName
End Sub

Screenshot