Converting a Linq expression tree that relies on SqlMethods.Like() for use with the Entity Framework
- by JohnnyO
I recently switched from using Linq to Sql to the Entity Framework. One of the things that I've been really struggling with is getting a general purpose IQueryable extension method that was built for Linq to Sql to work with the Entity Framework. This extension method has a dependency on the Like() method of SqlMethods, which is Linq to Sql specific. What I really like about this extension method is that it allows me to dynamically construct a Sql Like statement on any object at runtime, by simply passing in a property name (as string) and a query clause (also as string). Such an extension method is very convenient for using grids like flexigrid or jqgrid. Here is the Linq to Sql version (taken from this tutorial: http://www.codeproject.com/KB/aspnet/MVCFlexigrid.aspx):
public static IQueryable<T> Like<T>(this IQueryable<T> source,
string propertyName, string keyword)
{
var type = typeof(T);
var property = type.GetProperty(propertyName);
var parameter = Expression.Parameter(type, "p");
var propertyAccess = Expression.MakeMemberAccess(parameter, property);
var constant = Expression.Constant("%" + keyword + "%");
var like = typeof(SqlMethods).GetMethod("Like",
new Type[] { typeof(string), typeof(string) });
MethodCallExpression methodExp =
Expression.Call(null, like, propertyAccess, constant);
Expression<Func<T, bool>> lambda =
Expression.Lambda<Func<T, bool>>(methodExp, parameter);
return source.Where(lambda);
}
With this extension method, I can simply do the following:
someList.Like("FirstName", "mike");
or
anotherList.Like("ProductName", "widget");
Is there an equivalent way to do this with Entity Framework?
Thanks in advance.
