User503812343 posted
try below code on button click event
Protected Sub btnUpload_Click(ByVal sender As Object, ByVal e As EventArgs)
Dim validFileTypes As String() = {"pdf"}
Dim ext As String = System.IO.Path.GetExtension(FileUpload1.PostedFile.FileName)
Dim isValidFile As Boolean = False
For i As Integer = 0 To validFileTypes.Length - 1
If ext = "." & validFileTypes(i) Then
isValidFile = True
Exit For
End If
Next
If Not isValidFile Then
Label1.ForeColor = System.Drawing.Color.Red
Label1.Text = "Invalid File. Please upload a File with extension " & String.Join(",", validFileTypes)
Else
Label1.ForeColor = System.Drawing.Color.Green
Label1.Text = "File uploaded successfully."
End If
