title: How to insert null values to a Uniqueidentifier Column
body: <p>In my C# project I need to insert some null values to a UniqueIdentifier column.</p>
  
  <p>For fields city Guid, state Guid fields I should be able to insert null values 
  if there is no value(uniqueidentifier) available.
  I am getting the following error</p>
  
  <p>"Conversion failed when converting from a character string to uniqueidentifier."</p>
  
  <p>here is my code.</p>
  
  <pre><code>   string Query = @"INSERT INTO mytable
                              (table_GUID,
                              Date,
                              city_GUID,
                              state_GUID,                            
                              ) 
  
                          VALUES
                          ('" + tableGUID + @"', 
                          '" + Date + @"',  
                          '" + cityGUID + @"',
                          '" + stateGUID + @"'
                      )                       
  
   string insert = sql.executeNonQuery(Query);
  </code></pre>