Get reference to entity by string?

Question

In code I want to get reference to entity by name(string) without hardcoding it ApplicationData.TestEntity...

any ideas how this can be achieved?

Answer 1

The APIs for most of the concepts in LightSwitch provide a weakly-typed API in addition to the normally used strongly-typed API.  You're asking to make use of the weakly-typed API.  You can access the weakly-typed API by navigating to the Details property on the object in question.  In your example, you want to access, in a weakly-typed manner, the "TestEntities" entity set from the "ApplicationData" data service.  To do this you would write code like the following:

IEntitySet entitySet = (IEntitySet)this.ApplicationData.Details.Properties["TestEntities"].Value;

The Details object allows you to get all sorts of advanced information about the object from which you retrieved it.  Most of the objects in LightSwitch have such a Details object, including entities, screens, and even each of the properties of an entity or screen.  So you could write your whole application in a weakly-typed manner if you really wanted.

Answer 2

Wonderful!

The more dynamic, the better.

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Garth Henderson - Vanguard Business Technology

Answer 3

Just for illustrating how brilliant this weakly-typed API is:

Following extension method allows you to retrieve a entity based on the weakly typed entity type (e.g. "Customers") and the Key Segment (the Id field in most cases).

 public static class DataServiceExtensions
    {
        public static IEntityObject GetEntityByKey(this IDataService dataService,
string entitySetName, params object[] keySegments)
        {
            ICreateQueryMethod singleOrDefaultQuery = dataService.Details.Methods[entitySetName +
 "_SingleOrDefault"] as ICreateQueryMethod;
 
            if (singleOrDefaultQuery == null)
            {
                throw new ArgumentException("An EntitySet SingleOfDefault query does
not exist for the specified EntitySet.", entitySetName);
            }
 
            ICreateQueryMethodInvocation singleOrDefaultQueryInvocation = singleOrDefaultQuery.CreateInvocation(keySegments);
 
            return singleOrDefaultQueryInvocation.Execute() as IEntityObject;
        }
 
    }

So, it can be called as follows:

IEntityObject entityObject = this.DataWorkspace.ApplicationData.GetEntityByKey("Customers", 45);
 

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paul van bladel