Parse string into a LINQ query

Question

What method would be considered best practice for parsing a LINQ string into a query?

Or in other words, what approach makes the most sense to convert:

 string query = @"from element in source
                  where element.Property = ""param""
                  select element";

into

 IEnumerable<Element> = from element in source 
                        where element.Property = "param"
                        select element;

assuming that source refers to an IEnumerable<Element> or IQueryable<Element> in the local scope.

Answer 1

Starting with .NET 4.6 you can use CSharpScript to parse Linq. Assuming the expression you want to parse is in string variable "query", this will do it:

string query = "from element in source where element.Property = ""param"" select element";
IEnumerable result = null;
try 
{
    var scriptOptions = ScriptOptions.Default.WithReferences(typeof(System.Linq.Enumerable).Assembly).WithImports("System.Linq");
    result = await CSharpScript.EvaluateAsync<IEnumerable>(
             query,
             scriptOptions,
             globals: global);
} catch (CompilationErrorException ex) {
//
}

Don't forget to pass your (Data)source you want to work on, with the global-variable(s) to have access to them in script parsing.

Answer 2

It requires some text parsing and heavy use of System.Linq.Expressions. I've done some toying with this here and here. The code in the second article is somewhat updated from the first but still rough in spots. I've continued to mess round with this on occasion and have a somewhat cleaner version that I've been meaning to post if you have any interest. I've got it pretty close to supporting a good subset of ANSI SQL 89.