Call linqkit expression in a dynamic linq query

Question

How I can call this LinqKit expression

    public static Expression<Func<Transaction, string>> ExpressionOfStatusName
    {
        get
        {
            Expression<Func<Transaction, string>> status =
                (transaction) =>  transaction.TransactionStatus.Name;
            return status;
        }
    }

in a dynamic linq query (Linq as a string using System.Linq.Dynamic from Microsoft)

This expression works well in a standard Linq query like this

Expression<Func<Transaction, string>> expressionOfStatusName = Transaction.ExpressionOfStatusName;

var ex = from transaction in context.Transaction.AsExpandable()
         select expressionOfStatusName.Invoke(transaction)

But when I try to call it from a dynamic linq query, I receive an error "No applicable method 'Invoke' exists in type 'Expression`1' I have tried to add the linqkit import in the file System.Linq.Dynamic but it is still not working.

I want to be able to do something like that

var ex = context.Transaction.AsExpandable()
.Select (transaction=>transaction)
.Select("new { test = expressionOfStatusName.Invoke(transaction)");

Thank you for your help

score 0 · Answer 1 · answered Jul 30 '13 at 13:55

0

Linq expects Expression of func. You can use the MS Linq.Dynamic extension which takes strings and converts them to an Expression tree. Or you can use any tool you like to build the expression tree. The MS dynamic linq extension however parses a limited set of String inputs. Some sample docu/blog You are asking it to parse expressionOfStatusName.Invoke(transaction)" I dont think it can do that. You can debug the source to check. But i recall seeing simple membership analysis in there. The source is here

Furthermore I think you are pushing the limits on acceptable anonymous type input, once you get passed the parse challenge. anonymous types and Linq

answered Jul 30 '13 at 13:55

phil soady

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I am already using MS Linq.Dynamic I am trying to modify the source, I am trying to change the function FindMethod to call the LinqKit method: `int FindMethod(Type type, string methodName, bool staticAccess, Expression[] args, out MethodBase method) { if (methodName == "Invoke") { method = typeof(LinqKit.Extensions) .GetMethods() .Where(o => o.Name == "Invoke").First(); return 1; } [...]` but it returns an error Methods on type 'Extensions' are not accessible. – user1756338 Jul 30 '13 at 14:30
i noticed..... you tried to feed it "new { test = expressionOfStatusName.Invoke(transaction)". Please read answer again. Was I unclear somewhere ? – phil soady Jul 30 '13 at 14:32

Call linqkit expression in a dynamic linq query

1 Answers1