Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim readValue As String
 
        readValue = My.Computer.Registry.GetValue _
        ("HKEY_CLASSES_ROOT\" & TextBox1.Text, "", "ExtensionNotFound")
        MsgBox("The value is " & readValue)
 
    End Sub

Imports Microsoft.Win32
 
Public Shared Function GetFileType(ByVal fileExtension As String) As String
 
        Dim fileType As String = ""
 
        'Search all keys under HKEY_CLASSES_ROOT
        For Each subKey As String In Registry.ClassesRoot.GetSubKeyNames()
            If String.IsNullOrEmpty(subKey) Then
                Continue For
            End If
 
            If subKey.CompareTo(fileExtension) = 0 Then
                'File extension found. Get Default Value
                Dim defaultValue As String = Registry.ClassesRoot.OpenSubKey(subKey).GetValue("").ToString()
 
                If defaultValue.Length = 0 Then
                    'No File Type specified
                    Exit For
                End If
 
                If fileType.Length = 0 Then
                    'Get Initial File Type and search for the full File Type Description
                    fileType = defaultValue
                    fileExtension = fileType
                Else
                    'File Type Description found
                    If defaultValue.Length > 0 Then
                        fileType = defaultValue
                    End If
 
                    Exit For
                End If
            End If
 
        Next
 
        Return fileType
 
End Function
 
'Example USAGE
Dim fileType = GetFileType(".txt")