file_handling in vb.net

Public Class Form1


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim f_name = "c:\" + Filename_box.Text + ".txt"
        Dim readobj As New System.IO.StreamReader(f_name)
        Dim combo As String
        combo = ComboBox1.Text
        If combo = "Read line by line" Then
            MsgBox(readobj.ReadLine)

        ElseIf combo = "read to end" Then
            RichTextBox1.Text = readobj.ReadToEnd()

        End If
        readobj.Close()
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim f_name = "c:\" + Filename_box.Text + ".txt"
        Dim writeobj As New System.IO.StreamWriter(f_name)
        If System.IO.File.Exists(f_name) = True Then
            writeobj.Write(RichTextBox1.Text)
            MsgBox("Written to file")
        Else
            System.IO.File.Create(f_name)
            MsgBox("file " & f_name & " created ")
            writeobj.Write(RichTextBox1.Text)
        End If

        writeobj.Close()
    End Sub

    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
        Dim f_name = "c:\" + Filename_box.Text + ".txt"
        Dim appendobj As New System.IO.StreamWriter(f_name)
        Dim combo As String


        If System.IO.File.Exists(f_name) = True Then
            combo = ComboBox2.Text
            If combo = "Append from same line" Then

                appendobj.Write(RichTextBox1.Text)
                Button3.Visible = True
            ElseIf combo = "Append from next line" Then

                appendobj.WriteLine(RichTextBox1.Text)
                Button3.Visible = True
            End If
        Else
            MsgBox("file" & f_name & "doesn't exists !!!")
        End If

        appendobj.Close()
    End Sub


    Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
        Dim file1 As String
        Dim file2 As String
        file2 = "c:\" + copybox.Text + ".txt"
        file1 = "c:\" + Filename_box.Text + ".txt"
        System.IO.File.Copy(file1, file2)
        MsgBox("file " & file1 & " copied to " & file2)

    End Sub

    Private Sub Button6_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button6.Click
        Dim file1 As String
        Dim file2 As String
        file2 = "c:\" + movebox.Text + ".txt"
        file1 = "c:\" + Filename_box.Text + ".txt"
        System.IO.File.Move(file1, file2)
        MsgBox("file " & file1 & " moved to " & file2)
    End Sub

    Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
        Dim file As String
        file = "c:\" + Filename_box.Text + ".txt"
        If System.IO.File.Exists(file) = True Then
            System.IO.File.Delete(file)
            MsgBox("file " & file & " deleted")
        Else
            MsgBox("file " & file & " Doesn't exists")
        End If

    End Sub

    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        Button1.Visible = True

    End Sub

    Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
        Button3.Visible = True
    End Sub
    Private Sub copybox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles copybox.TextChanged
        Button4.Visible = True
    End Sub
 Private Sub movebox_TextChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles movebox.TextChanged
        Button6.Visible = True

End Sub
    End Class