C# – Access Linq result contained in a dynamic class

cdynamic-linqlinqlinq-to-sql

I'm using DbLinq which should be the equivalent of Linq2SQL for this question. I'm need to generate a Linq2SQL query where I specify the columns I want returned at runtime. I can achieve that using the Dynamic Linq extension methods but I can't work out how to extract the result.

string someProperty = "phonenumber";
string id = "1234";

Table<MyClass> table = context.GetTable<MyClass>();
var queryResult = (from item in table where item.Id == id select item).Select("new (" + someProperty + ")");

The Linq expression generates the proper SQL of:

select phonenumber from mytable where id = '1234'

And in the debugger I can see the phonenumber value is sitting there in the Results View. The problem is I can't work out how to get the phonenumber value from the queryResult object? The type of queryResult is:

QueryProvider<DynamicClass1>

Edit:
I discovered a way to do it but it seems very crude.

IEnumerator result = (from item in table where item.Id == id select item).Select("new (" + someProperty + ")").GetEnumerator();
result.MoveNext();
var resultObj = result.Current;
PropertyInfo resultProperty = resultObj.GetType().GetProperty(someProperty);
Console.WriteLine(resultProperty.GetValue(resultObj, null));

Perhaps someone knows a cleaner way?

Best Answer

Linq uses deferred execution method to get data. Deferred execution means that the evaluation of an expression is delayed until its realized value is actually required.

In your case queryResult is a IEnumerable object, which means no data has actually been evaluated yet. You can evaluate queryResult object by calling result.ToList() or result.ToDictionary(), or any other methods that will return an object with non-IEnumerable data types.

Hope this is helpful.

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