read word document(doc,docx) content to a string

You can use the DocumentFactory and Document Classes from LEADTOOLS to get the text from any supported document format (Doc, Docx, PDF, etc.) using the following lines of code:

using (var document = DocumentFactory.LoadFromFile(inFile, new LoadDocumentOptions()))
{
var page = document.Pages[0];
var pageText = page.GetText();
if (pageText != null)
{
pageText.BuildText();
var text = pageText.Text;
MessageBox.Show(text);
}
else
{
MessageBox.Show("Failed!");
}
}

More details can be found here:
https://www.leadtools.com/help/leadtools/v19m/dh/dox/documenttext.html