C# - VSTO - WriteCustomDocumentProperties

c#-vsto-writecustomproperties.cs

 private void WriteDocumentProperty(string propertyName, string value)
        {
            Microsoft.Office.Core.DocumentProperties properties;
            Document doc = this.getDoc();
            properties = (Microsoft.Office.Core.DocumentProperties)
                 doc.CustomDocumentProperties;
            if (properties.Cast<DocumentProperty>().Where(c => c.Name == propertyName).Count() == 0)
                properties.Add(propertyName, false, MsoDocProperties.msoPropertyTypeString, Guid.NewGuid().ToString());
            properties[propertyName].Value = value;

        }