AddOData() is not idempotent

[hfaran]

If .AddOData() is called twice, an exception is thrown. Similar to most other ASP.NET Core Add* methods, .AddOData() should be idempotent, but it is currently not.

Assemblies affected

• Microsoft.AspNetCore.OData.dll

Reproduce steps

• Call services.AddOData() twice in your Startup.ConfigureServices method.

Expected result

• No exception should be thrown; AddOData() should return the same IODataBuilder if called multiple times. The operation should be idempotent.

Actual result

The following exception is thrown on the second invocation of AddOData():

System.InvalidOperationException: 'Sequence contains no matching element'

Additional detail

An obvious suggestion to this may to be to "not call .AddOData() more than once". Sure, that would fix it, but we need to call it twice due to the way our framework is set up (the second call is required to get the IODataBuilder so that we can use aspnet-api-versioning).

[marabooy]

@hfaran Thanks for reporting this. found the issue is currently caused by the following lines https://github.com/OData/WebApi/blob/master/src/Microsoft.AspNetCore.OData/Extensions/ODataServiceCollectionExtensions.cs#L78-L87

[hfaran]

@marabooy Thanks for the ack.