Dynamic Linq query Contains List

You could write something like this that builds your query function dynamically:

public static Func<ObjT, bool> PropertyCheck<ObjT, PropT>(string propertyName, Expression<Func<PropT, bool>> predicate)
{
    var paramExpr = Expression.Parameter(typeof(ObjT));
    var propExpr = Expression.Property(paramExpr, propertyName);
    return Expression.Lambda<Func<ObjT, bool>>(Expression.Invoke(predicate, propExpr), paramExpr).Compile();
}

Then, it could be used like this:

foos.Where(PropertyCheck<Foo, int>("MyId", x => idList.Contains(x)));

Of course, you could also just provide your own Where extension method that does all that at once:

public static IEnumerable<T> Where<T, PropT>(this IEnumerable<T> self, string propertyName, Expression<Func<PropT, bool>> predicate)
{
    var paramExpr = Expression.Parameter(typeof(T));
    var propExpr = Expression.Property(paramExpr, propertyName);
    return self.Where<T>(Expression.Lambda<Func<T, bool>>(Expression.Invoke(predicate, propExpr), paramExpr).Compile());
}

foos.Where<Foo, int>("MyId", x => idList.Contains(x));

You could use the expressions to do this dynamic query, try something like this, for sample:

import these namespaces:

using System.Linq;
using System.Linq.Expressions;
using System.Reflection;

And try this:

// a reference parameter
var x = Expression.Parameter(typeof (YourType), "x");

// contains method
var containsMethod = typeof (string).GetMethod("Contains", new[] {typeof (string)});

// reference a field
var fieldExpression = Expression.Property(instance, "PropertyName");

// your value
var valueExpression = Expression.Constant(yourId);

// call the contains from a property and apply the value
var containsValueExpression = Expression.Call(fieldExpression, containsMethod, valueExpression);

// create your final lambda Expression
var filterLambda = Expression.Lambda<Func<YourType, bool>>(containsValueExpression, x);

// apply on your query
q = q.Where(finalLambda);

Obs: make sure your property has a method called contains.