How to implement method with expression parameter c#

Question

I want to create a method like this:

var result = database.Search(x=>x.Name, \"Entity Name field value\");
result = database.Search

        

Answer 1

You can turn a selector and value into a predicate using Expression.Equal:

static IQueryable Search(
    this IQueryable source,
    Expression> selector,
    TValue value)
{
    var predicate = Expression.Lambda>(
        Expression.Equal(
            selector.Body,
            Expression.Constant(value, typeof(TValue))
        ), selector.Parameters);
    return source.Where(predicate);
}

Then you just need to do something like:

var result = database.SomeEntities.Search(x => x.SomeProp, "value");

If you want to do it from the database, then that depends on what the database is; for example, with LINQ-to-SQL you could add an additional method:

static IQueryable Search(
    this System.Data.Linq.DataContext database,
    Expression> selector,
    TValue value) where TSource : class
{
    IQueryable source = database.GetTable();
    return Search(source, selector, value);
}

and use:

var result = database.Search(x => x.SomeProp, "value");

frankly I think it is clearer to use the database.SomeEntities version, though.