Question

Following a couple different tutorials, I’ve been trying to build a “Silverlight Business Application” against a database I’ve created. I’ve found I have two problems. The one I’m asking about here is how to filter the query.

The query that is built in the DomainService is when using the VS2010 template is:

[EnableClientAccess]
public class ChargesService : LinqToEntitiesDomainService<ChargesEntities>
{
    public IQueryable<tblChargeCode> GetCharges()
    {
        return ObjectContext.tblChargeCodes.OrderBy(e => e.Chrgs_Code_01).Take(10);
    }
}

I’m trying to create another query against the same ObjectContext.tblChargeCodes. Pulling the entire table (30 columns by ~7k rows) creates a timeout error.

I can’t figure out how to do a select. I want to select Charge_Codes_01 and Bill_Description with a “starts with” type functionality (dynamic drop down search functionality). I’ve tried different variations of this without success. Something just isn’t clicking in my brain.

    public IQueryable<tblChargeCode> SearchCharges(string num)
    {
        var min = System.Convert.ToInt32(num.PadRight(7, '0'));
        var max = System.Convert.ToInt32(num.PadRight(7, '9'));
        return ObjectContext.tblChargeCodes
            .Select(e => e.Chrgs_Code_01, e.Chrgs_Code_01_Desc)
            .Where(e => e.Chrgs_Code_01 >= min && e.Chrgs_Code_01 <= max)
            .OrderBy(e => e.Chrgs_Code_01)
            .Take(10);
    }

Answer 1

(sorry for my bad english)

The problem with you code is the “Select” – your method signature says that it must return a IQueryable of tblChargeCode, so you cannot return a projection. Here is two ways you can write your query:

In the server:

public IQueryable<tblChargeCode> SearchCharges(int min, int max, string description)
{        

    return ObjectContext.tblChargeCodes            
        .Where(e => e.Chrgs_Code_01 >= min && e.Chrgs_Code_01 <= max)
        .Where(e => e.Bill_Description.StartsWith(description))
        .OrderBy(e => e.Chrgs_Code_01)
        .Take(10);
}

And call it on the client:

context.Load(context.SearchChargesQuery(0, 9999999, "Bill"), (op) => 
{
    //op.Entities has your entities loaded
}, null);

Or you can just leave the query on the server:

public IQueryable<tblChargeCode> GetCharges()
{
    return ObjectContext.tblChargeCodes.OrderBy(e => e.Chrgs_Code_01);
}

And call it from the client (it will filter on the server)

context.Load(context.GetChargesQuery().Where(e => e.Chrgs_Code_01 >= 0 && e.Chrgs_Code_01 <= 9999999)
        .Where(e => e.Bill_Description.StartsWith("Bill"))
        .OrderBy(e => e.Chrgs_Code_01)
        .Take(10), (op) => 
        {
            //op.Entities has your entities loaded
        }, null);

You also can use “Contains” instead of “StartsWith” in your query.