Support Enums as Keys in OData Client

[WanjohiSammy]

Issues

This pull request fixes #2964.

Description

This change involves adding functionality to support the use of enumeration types as keys.

Currently, attempting to query entities with enums as keys through OData Client, results in an error stating that the operation is not valid for non-generic types.

Exception:
This operation is only valid on generic types.

Change:
This modification will address this issue, allowing enums as keys without causing exceptions.
For example, the below Employee object has EmpType which is a key of Type Enum and NullableEmpType which is nullable generic Type with Enum as generic argument.

public class Employee
{
    [System.ComponentModel.DataAnnotations.Key]
    public int EmpNumber { get; set; }

    // Enum - Employee Type Key
    [System.ComponentModel.DataAnnotations.Key]
    public EmployeeType EmpType { get; set; }

    [System.ComponentModel.DataAnnotations.Key]
    public EmployeeType? NullableEmpType { get; set; }

    public string Name { get; set; }

    public decimal Salary { get; set; }
}

public enum EmployeeType
{
    Hybrid = 1,
    FullTime = 2,
    PartTime = 3
}

Checklist (Uncheck if it is not completed)

• Test cases added
• Build and test with one-click build and test script passed

Additional work necessary

If documentation update is needed, please add "Docs Needed" label to the issue and provide details about the required document change in the issue.

[habbes]

I think it would be good to add a test that shows that querying data by keys with enum executes corectly without throwing an exception, just to make sure that the big-picture scenario that is describe in the original issue is resolved.

[WanjohiSammy]

I think it would be good to add a test that shows that querying data by keys with enum executes corectly without throwing an exception, just to make sure that the big-picture scenario that is describe in the original issue is resolved.

@habbes Yes, this can be done. However, I have added tests on the specific methods that are called when getting KeyProperties. GetKeyProperties() method is the one that was throwing exception when enum was used as keys.

test/FunctionalTests/Microsoft.OData.Client.Tests/Metadata/ClientTypeUtilTests.cs

[gathogojr]

#3013 (comment)

@WanjohiSammy Probably add a test(s) to verify that nullable properties are not permitted (other than nullable enum property). Also create an issue to fix it in next major release such that no nullable property area allowed. We published ODL 8 RC so I don't think we can sneak in the change in ODL 8

[WanjohiSammy]

#3013 (comment)

@WanjohiSammy Probably add a test(s) to verify that nullable properties are not permitted (other than nullable enum property). Also create an issue to fix it in next major release such that no nullable property area allowed. We published ODL 8 RC so I don't think we can sneak in the change in ODL 8

@gathogojr I already added a test for this case where I am using a Key of Type struct. This will throw an exception.
IFTypeProperty_HasNullableGenericTypeKey_OfTypeStruct_GetKeyPropertiesOnType_ThrowsException()

[WanjohiSammy]

I think it would be good to add a test that shows that querying data by keys with enum executes corectly without throwing an exception, just to make sure that the big-picture scenario that is describe in the original issue is resolved.

@habbes Thanks for this. I have added these tests in the file test/FunctionalTests/Microsoft.OData.Client.Tests/Tracking/DataServiceContextQueryTests.cs

[mikepizzo]

Thanks for the contribution and follow-up on feedback.