HowTo: Use the Microsoft Word Object Model capabilities for spell checking

The Microsoft Word Object Model contains a lot of capabilities that .NET developers can benefit from. While everybody knows about the abilities of Microsoft Word related to text formatting, few are aware of its rich capacity in the spell check area.

Let’s try to make use of this capacity now. We will need a Microsoft Word COM addin in which we use an ordinary .net form with the RichTextBox control and two Buttons. You type some text into the RichTextBox, later on this text will be spell checked on a button click. The code of button click event handler is shown below:

Private Sub btnRun_Click(ByVal sender As System.Object, ByVal e _
  As System.EventArgs) Handles btnRun.Click
    Dim addinModuleObj As AddinModule = TryCast _
      (AddinModule.CurrentInstance, AddinModule)
 
    richTextBox.SelectAll()
    richTextBox.SelectionColor = Color.Black
    Dim Template As Object = Type.Missing
    Dim NewTemplate As Object = Type.Missing
    Dim DocumentType As Object = Type.Missing
    Dim Visible As Object = False
    Dim docs As Word.Documents = addinModuleObj.WordApp.Documents
    If docs IsNot Nothing Then
        Try
            Dim document As Word._Document = docs.Add(Template, _
              NewTemplate, DocumentType, Visible)
            If document IsNot Nothing Then
                Try
                    Dim range As Word.Range = document.Content
                    If range IsNot Nothing Then
                        Try
                            range.Text = richTextBox.Text
                            Dim Count As Integer = _
                              FindSpellingErrors(document)
                            Dim SaveChanges As Object = _
                              Word.WdSaveOptions.wdDoNotSaveChanges
                            Dim OriginalFormat As Object = Type.Missing
                            Dim RouteDocument As Object = Type.Missing
                            document.Close(SaveChanges, OriginalFormat, _
                              RouteDocument)
                            If Count = 0 Then
                                MessageBox.Show("There are no errors!", _
                                  "Add-in Express HowTo")
                            Else
                                MessageBox.Show(String.Format( _
                                  "{0} Error(s) were found!", Count), _
                                  "Add-in Express HowTo")
                            End If
                        Finally
                            Marshal.ReleaseComObject(range)
                        End Try
                    End If
                Finally
                    Marshal.ReleaseComObject(document)
                End Try
            End If
        Finally
            Marshal.ReleaseComObject(docs)
        End Try
    End If
End Sub

And here is the FindSpellingErrors method used in the code above:

Private Function FindSpellingErrors(ByVal document As Word._Document) _
  As Integer
    Dim ret As Integer = 0
    document.SpellingChecked = False
    Dim spellingErrors As Word.ProofreadingErrors = TryCast( _
      document.SpellingErrors, Word.ProofreadingErrors)
    If spellingErrors IsNot Nothing Then
        Try
            ret = spellingErrors.Count
            For i As Integer = 1 To spellingErrors.Count
                Dim itemError As Word.Range = spellingErrors.Item(i)
                If itemError IsNot Nothing Then
                    Try
                        richTextBox.Find(itemError.Text, _
                          itemError.Start, _
                          RichTextBoxFinds.MatchCase Or _
                          RichTextBoxFinds.WholeWord)
                        richTextBox.SelectionColor = Color.Red
                    Finally
                        Marshal.ReleaseComObject(itemError)
                    End Try
                End If
            Next
        Finally
            Marshal.ReleaseComObject(spellingErrors)
        End Try
    End If
    Return (ret)
End Function

There is one unpleasant thing about the ProofreadingErrors collection – it is slow. I don't know the exact reason why it is so, I just feel a caveat should be made about this.

Also note that you can use the capabilities of the Word Object Model not only from inside of a COM add-in, but in a standalone application as well.

You may also be interested in:

Creating Word COM add-in step-by-step

Available downloads:

The sample add-ins below were written using Add-in Express 2008 for Office and .net

C# sample Word add-in for VS 2005
VB.NET sample Word add-in for VS 2005