Fix: The argument types 'Edm.Guid' and 'Edm.String' are incompatible for this operation.

This one had me going for a while until I found the tip in Julie Lerman’s essential book,  Programming Entity Framework, 2nd Edition.

In my ASP.NET 4 project, I create an Entity SQL query to look up a GUID. I cast the GUID as a string and wrap it in single quotes like this (non-working code):

strwhere = "(it.BusActivityID=" & busActivityID.ToString & _
        " AND it.UserID='" & mem.ProviderUserKey.ToString() & "' )"

This produces the following error message:

“The argument types 'Edm.Guid' and 'Edm.String' are incompatible for this operation. Near equals expression, line 6, column 34. “

The fix is to escape the GUID for Entity SQL. You jam in the escape literal GUID and a space  just before the quoted GUID string:

strwhere = "(it.BusActivityID=" & busActivityID.ToString & _ 
  " AND it.UserID=GUID '" & mem.ProviderUserKey.ToString() & "' )"

It turns out there are a whole whack of these escape keyword/literal thingies listed here:

Literals (Entity SQL)

http://msdn.microsoft.com/en-us/library/bb399176.aspx

Sheesh. Why do I lose time on things like this?

Ken