Accessing results after Dynamic.dll Query on Column Names

Question

Hi,

The following dynamic query works fine in LINQPad, but I have a problem accessing the contents of the resulting IEnumerable<TResult>. My table has many fields, and I use the dynamic query to select a specific set, but I can't figure out how to address the returned fields. The alternative I then had to resort to, was using "ExecuteQuery" ... I'd prefer to get it working with dynamic LINQ. Any tips?

String nameX = "ubutu";
var x = It_StdUnit_Types
    .Where(t => t.cl1 == 1000)
    .Select("new(_KID," + nameX + ")");
x.Dump("ok, got the contents of nameX");

but when I try to do a foreach(x...), the x will be enumerated, but I can't see/access any column names...

Thanks!
R

---

Hubert-Associates

Answer 1

.Select("new(.... will project into a runtime generated type. It is not known/defined at design/compile time so you need to use reflection to access the members.

E.g.:

foreach (object o in x)
{
    string nameXValue = GetPropertyValue(o, nameX);
}

...

public object GetPropertyValue(object obj, string propName)
{
    System.Reflection.PropertyInfo propInfo = obj.GetType().GetProperty(propName);
    return propInfo.GetValue(obj, null);
}

---

Kristofer - Huagati Systems Co., Ltd.
Cool tools for Linq-to-SQL and Entity Framework:
huagati.com/dbmltools (add-in with new features for Visual Studio 2008's L2S and EF designers)
huagati.com/L2SProfiler (Query profiler for Linq-to-SQL and LLBLGen Pro)

Answer 2

Thanks. Great answer! After playing with this a bit, it works fine, but apparently there is no .First() operator with Dynamic.dll. So how can I get this to work if I only want a single/first-hit record?

---

Hubert-Associates

Answer 3

Hi Hubert,

 

You can use the Take(1) extension method in the Dynamic.dll to retrieve the first object. 

===============================================================================
        public static IQueryable Take(this IQueryable source, int count) {

            if (source == null) throw new ArgumentNullException("source");

            return source.Provider.CreateQuery(

                Expression.Call(

                    typeof(Queryable), "Take",

                    new Type[] { source.ElementType },

                    source.Expression, Expression.Constant(count)));

        }
===============================================================================

 

Have a nice day!

 

 

Best Regards,
Lingzhi Sun

MSDN Subscriber Support in Forum

If you have any feedback on our support, please contact [e-mail]

---

Please remember to mark the replies as answers if they help and unmark them if they provide no help.
Welcome to the All-In-One Code Framework! If you have any feedback, please tell us.