CRM 2011 LINQ Operator Limitations:

.       from

–       Supports one from clause per query.

•          join

–       Represents an inner join. You cannot perform outer joins.

•          where

–      The left side of the clause must be an attribute name and the right side of the clause must be a value.

–      Supported String functions: Contains, StartsWith, EndsWith, and Equals.

•          groupBy

–      Not supported. FetchXML supports grouping options that are not available with the LINQ query provider.

–      For more information, see Use FetchXML Aggregation.

•          orderBy

–       Supports ordering by entity attributes, such as Contact.FullName.

•          select

–       Supports anonymous types, constructors, and initializers.

•          last

–       The last operator is not supported.

•          skip and take

–       Supports skip and take using server-side paging. The skip value must be greater than or equal to the take value.

•          aggregate

–       Not supported. FetchXML supports aggregation options that are not available with the LINQ query provider. For more information, see Use FetchXML Aggregation.