如何在VB.net的“打开文件”对话框中包含消息框

Question

In my previous question: How to know if the file I'm opening is a .txt file or not in VB.net

I ask here how to know if I'm opening .txt file or not.

The code below is my code for opening a .txt file and prompt the user if the file is .txt of not.

Dim filename As String = String.Empty
Dim TextLine As String = ""
Dim SplitLine() As String


Dim ofd1 As New OpenFileDialog()

ofd1.Filter = "txt files (*.txt)|*.txt|All files (*.*)|*.*"
ofd1.FilterIndex = 2
ofd1.RestoreDirectory = True
ofd1.Title = "Open Text File"

'get the filename of the txt file
If ofd1.ShowDialog() = DialogResult.OK Then
'if the file is not .txt file
        If (Path.GetExtension(filename).ToLower() <> ".txt") Then
            MessageBox.Show("Please select text Files only", _
                            "RMI", _
                             MessageBoxButtons.OK, _
                             MessageBoxIcon.Warning)

            'show the open file dialog
            ofd1.ShowDialog()

            'if the file is .txt file
        Else
            filename = ofd1.FileName
 End If

'if the filename is existing
If System.IO.File.Exists(filename) = True Then

    Dim objReader As New System.IO.StreamReader(filename)

    'read the text file and populate the datagridview
    Do While objReader.Peek() <> -1
        TextLine = objReader.ReadLine()
        TextLine = TextLine.Replace(" ", "")
        SplitLine = Split(TextLine, ",")
        dvList.Rows.Add(SplitLine)
    Loop

End If

If the file that I selected is not .txt file, here is the output:

If I open a file that is not existing, here is the output:

In the 1st image, it only show the error message box, but in the 2nd image, the error message box is within the open file dialog.

My question is how can I show the error message box of the 1st image with the open file dialog?

Thank you.

Answer 1

Notes:

• No need to check the extension after you show the form, but you should instead set the appropriate filter in order to limit the selection of .txt files only "txt files (*.txt)|*.txt"
• You can use the OpenFileDialiog.CheckFileExists and OpenFileDialiog.CheckPathExists properties to prevent user to enter an invalid file name/path (display an error message)
• Not sure you need to check a second time if the file exists if you use CheckFileExists / CheckPathExists
• You should always dispose a form that you show using ShowDialog() method.
• You should dispose the StreamReader

---

Dim filename As String = String.Empty
Dim TextLine As String = ""
Dim SplitLine() As String

Using ofd1 As New OpenFileDialog()
        ofd1.Filter = "txt files (*.txt)|*.txt"
        ofd1.FilterIndex = 2
        ofd1.CheckPathExists = True
        ofd1.CheckPathExists = True
        ofd1.RestoreDirectory = True
        ofd1.Title = "Open Text File"

        'get the filename of the txt file
        If ofd1.ShowDialog() = DialogResult.OK Then
            filename = ofd1.FileName

            Using objReader As New System.IO.StreamReader(filename)

                'read the text file and populate the datagridview
                Do While objReader.Peek() <> -1
                    TextLine = objReader.ReadLine()
                    TextLine = TextLine.Replace(" ", "")
                    SplitLine = Split(TextLine, ",")
                    dvList.Rows.Add(SplitLine)
                Loop
            End Using
        End If
End Using

Answer 2

Here i add the label which is hidden. (name: pathlabel) button (open file) add openfiledialog from toolbox

this is so simple. Open File button:

openfiledialog.showdialog()

OpenFileDialog_FileOk :

PathLabel.Text = System.IO.Path.GetExtension(OpenFileDialog.FileName)
    If PathLabel.Text = ".txt" Then
        Dim Objectreader As New System.IO.StreamReader(OpenFileDialog.FileName)
        TextBox1.Text = Objectreader.ReadToEnd
        Objectreader.Close()
    Else
        MsgBox("please select only Text Document (.txt)", MsgBoxStyle.Critical + MsgBoxStyle.OkOnly, "Error")
    End If

Thank you...

---

Instead of this you must set the filter to openfiledialog button code (open file)

Openfiledialog.showdialog()
openfiledialog.filter = "Text Document|*.txt"