Dynamically sorting a DbDataReader using LINQ

I am very new to LINQ and have a class method, which when called, returns a DbDataReader object. How would I sort开发者_开发问答 this dynamically using a LINQ query expression where the sort expression is provided as a string (e.g. "LastName DESC")

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Can't take any credit - links in this question to Dynamic Linq and how to do it without:

Dynamic LINQ OrderBy on IEnumerable<T>