Question

I am trying to convert a Linq query that I have working in Linq to be able to work in dynamic linq (using System.Linq.Dynamic) because I want a user to be able to form their own queries and this query string would be added onto other query strings at runtime.

I have a query:

db.incidents.Where(a => a.incidentLocations.Single().location.street.Contains(location);

and I have tried to convert it to the following dynamic linq string:

query = 
string.Concat("incidentLocations.Single().location.street.Contains(\"", location, "\")");

db.incidents.Where(query);

Where location is a string that includes search text.

I have managed to convert all my other queries to dynamic linq but this one i am struggling with the exception error:

“No applicable aggregate method ‘Single’ exists”

I understand that dynamic linq does not support all extension methods, could someone possibly tell me how I could get round this problem.

Answer 1

Get the source of Linq.Dynamic, copy paste the Where method, change the signature and the string with the function name inside the method and you’re good to go. I did it to add Single First etc, I can’t copy it here because I’m not on my dev machine but I’ll do it later if necessary 😉

EDIT: here’s the Single method if you decide to use it:

public static object Single(this IQueryable source)
    {
        if (source == null) throw new ArgumentNullException("source");
        return source.Provider.Execute(
            Expression.Call(
                typeof(Queryable), "Single",
                new Type[] { source.ElementType },
                source.Expression));
    }