Dapper.Contrib | Dapper community contributions - additional extensions

While mapping your models, be bit more explicit. Mention the Schema explicitly.
Following is an example how to provide various mapping properties.

You can use the TableAttribute of the Dapper.Contrib.Extensions namespace.

This is not caused by Dapper, it is caused by JsonSerializer accessing the property.

If you add the [JsonIgnore] attribute to your property then it will not be accessed by JsonSerializer

I believe what is happening is you are using a mocked connection and trying to call a Dapper method, InsertAsync, on it. The Dapper method is inevitably failing because it is not a real connection.

I'm not sure how much value you get using mocks here. What you really want to know, when testing AddAsync, is does it actually do what you want it to do which is insert data into the database. So if I were you I would turn this test into an integration test by using a real connection instead of a mocked one. One way of doing this is to

1. Use a test database for the purposes of testing
2. Before running the test delete all data from the test database
3. In your assert use Dapper or otherwise to check that a query for the entity brings back the data you expect to be in the database.

I don't necessarily recommend this but another approach could be to use an in memory database. See for example unit testing Dapper Repositories.

Turns out it was a type mismatch that slipped my eyes. Since the signature of IDbConnectionExtensionsWrapper.Get(...) takes an int? and I was setting up the mock with It.IsAny(), there was no suitable call to the method (it was never called).

The correct way to mock the method would be

Your implementation has a couple of problems but, because you're essentially returning type.Name, it should be returning the name of your type (in this case Student).

First let's address the problems with your current implementation of TableNameMapper;

1. You only need to set the delegate once. You can do this somewhere like the ConfigureServices of your Startup class. Right now you're setting it everytime you open your connection.

2. Your implementation executes type.Name.Remove(type.Name.Length - 1, 1); but you're not assigning the result of the operation to a variable. Even if you had assigned the result you're just returning type.Name anyway.

I ran the code you have above and it works correctly for me in LINQPad. I'd suggest adding a breakpoint in your debugger on the return type.Name; line of your delegate. If you need a hand debugging then take a look at the Visual Studio debugging documentation. Check what type.Name actually is and go from there.

Here's the code I ran verbatim:

Remove the Microsoft.AspNetCore.* nuget packages, those no longer exist in 3.0 so you're pulling in 2.x versions. https://docs.microsoft.com/en-us/aspnet/core/migration/22-to-30?view=aspnetcore-3.1&tabs=visual-studio#remove-obsolete-package-references