Simplest code to OCR an image using Microsoft Office's Imaging functionality (requires MS-Office 2007 or later, imaging components must be installed and MODI must be added to references).

private string OCR ( string fileToOCR)
{
MODI.Document md = new MODI.Document();

md.Create(fileToOCR);
md.OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true);
MODI.Image img = (MODI.Image) md.Images[0];
MODI.Layout layout = img.Layout;
layout = img.Layout;
string result = layout.Text;
md.Close (false);

return result;

}

Calling function can be:
private void button6_Click(object sender, EventArgs e)
{
MessageBox.Show ( OCR ("C:\\temp\\in.tif"));
}