Currently I have a C# Silverlight business application which uses RIA Services. The application is hosted in ASP.NET using the ADO.NET Entity Framework and a domain service class to read and write to the SQL Server database.
I have a server-side method in my DomainServiceClass that returns an IEnumerable list of objects. In my ApplicationName.Web.g.cs file I have an autogenerated function too. In my Silverlight Client Application I want to be able to run a foreach loop over the returned list of objects.
public IEnumerable<Image> GetJobImages(string jobGuid)
{
var query =
(
from j in Context.Job
orderby (j.ShortCode)
where j.JobID.Equals(jobGuid)
join a in Context.Audit //.Distinct()
on j.JobID equals a.Job.JobID
join i in Context.Image
on a.Image.JobID equals i.JobID
select new Image
{
HighResUrl = i.HighResUrl,
LowResUrl = i.LowResUrl,
UploadDate = i.UploadDate
}).AsEnumerable();
return query;
}
/// <summary>
/// Returns an EntityQuery for query operation 'GetJobImages'.
/// </summary>
public EntityQuery<Image> GetJobImagesQuery(string jobGuid)
{
Dictionary<string, object> parameters = new Dictionary<string, object>();
parameters.Add("jobGuid", jobGuid);
return base.CreateQuery<Image>("GetJobImages", parameters, false, true);
}
var context = dds.DomainContext as InmZenDomainContext;
foreach(var item in context.GetJobImagesQuery(currentJob.JobID.ToString())
{
item.etc.....//
}
Unfortunately When I try and invoke this method as above, I receive either the error:
'Cannot implicitly convert type System.Windows.Ria.Data.EntityQuery to System.Collections.IEnumerable'.
OR
'Does not contain a public definition for GetEnumerator'.
After reading and talking to others, I have been informed that I need to change the return type on the AutoGenerated Function (I think).
Does anyone know of a way in which I can change the return type to IEnumerable on this AutoGenerated EntityQuery?! - Or of a different way in which to solve this problem?
/// <summary>
/// Returns an EntityQuery for query operation 'GetJobImages'.
/// </summary>
public IEnumerable<Image> GetJobImagesQuery(string jobGuid)
{
Dictionary<string, object> parameters = new Dictionary<string, object>();
parameters.Add("jobGuid", jobGuid);
return base.CreateQuery<Image>("GetJobImages", parameters, false, true);
}
(This fails since the method is autogenerated, it just springs back to what it used to be when I build the solution.)
Help greatly appreciated.
The problem is that you're missing a step between your call and the IEnumerable collection.
You need to execute the EntityQuery and use LoadOperation to get your results. It's not as straightforward as you'd think, and here's a good forum post that has an example of how to handle things:
How to get a List<> from LoadOperation
Here's the relevant line from the example:
EntityQuery query = Context.GetEmployeesQuery();
Context.Load<Employee>(query).Completed += (sender, args) => {
List<Employee> list = ((LoadOperation<Employee>)sender).Entities.ToList();
};
You need to load the query and get the results from the load operation. Your Silverlight client invocation code should be modified into something like this:
var context = dds.DomainContext as InmZenDomainContext;
var loadOperation = context.Load(context.GetJobImagesQuery(currentJob.JobID.ToString()));
loadOperation.Completed += (sender, e) => {
if (!loadOperation.HasError)
foreach (var item in loadOperation.Entities)
// Loop over returned items ... Or use LINQ on loadOperation.Entities.
else
// loadOperation.Error has details about the error.
...
}
Note that all "network calls" are asynchronous in Silverlight.
I would also suggest that you consider changing the query parameter from a string into a GUID.