DataSource.Table.Where(stringOfConstraint) does not exist in LinqToSQL for OData support?

I'm looking at this Telerik demo, and am unable to get the "count" statement to work. I believe that the following command is only supported on EntityFramework, and not Linq2SQL.

return  CurrentDataSource.Products.Where(where).Count();

The parameter "where" in lowercase is actually a string that is passed in the ADO.Net DataServices (OData) url. This URL should be sent to the Linq provider to furthe开发者_JAVA技巧r constrain the query.

If that is not supported in Linq2SQL, how can I make a similar statement?

You need to use a lambda expression for the predicate used by the Queryable.Where method:

return CurrentDataSource.Products.Where(p => p.Id > 100).Count();

If you really want to use a string then take a look at Dynamic LINQ, starting with Scott Gu's blog post: Dynamic LINQ (Part 1: Using the LINQ Dynamic Query Library). Then you should be able to write queries similar to:

return CurrentDataSource.Products.Where("Id > 100").Count();

You could write your own generic extension, how you should write the most effective one depends on the situation... but it should probably be something like:

public static class IQueryableExtensions 
{
    public static int Count(this IQueryable<T> query)
    {
       return query.ToList().Count;
    }
}

This is probably not the most effective way and only works if you have an IQueryable. If performance is not a problem just use it.