问调试.net核心IModelBinder有Visual跳线

EN

public class JsonModelBinder : IModelBinder
{
    private readonly IOptions<MvcJsonOptions> _jsonOptions;
    private readonly ILoggerFactory _loggerFactory;

    public JsonModelBinder() { }

    public JsonModelBinder(IOptions<MvcJsonOptions> jsonOptions, ILoggerFactory loggerFactory)
    {
        _jsonOptions = jsonOptions;
        _loggerFactory = loggerFactory;
    }

    public Task BindModelAsync(ModelBindingContext bindCtx)
    {
        string modelName = bindCtx.ModelName;

        ValueProviderResult valueProviderResult = bindCtx.ValueProvider.GetValue(modelName);

        if (valueProviderResult == ValueProviderResult.None)
        {
            return Task.CompletedTask;
        }

        bindCtx.ModelState.SetModelValue(bindCtx.ModelName, valueProviderResult);

        string value = valueProviderResult.FirstValue;

        if (string.IsNullOrEmpty(value))
        {
            return Task.CompletedTask;
        }

        JToken token;

        try
        {
            token = JToken.Parse(value);
        }
        catch (JsonReaderException)
        {
            bindCtx.ModelState.TryAddModelError(modelName,  "Invalid json object.");
            return Task.CompletedTask;
        }
        catch (Exception ex)
        {
            bindCtx.ModelState.TryAddModelError(modelName, ex.Message);
            return Task.CompletedTask;
        }
        bindCtx.Result = ModelBindingResult.Success(token);
        return Task.CompletedTask;
    }
}

public class JsonModelBinderFacts
{
    [Fact]
    public async Task BindModelAsync_WithNullValueProvider_SetsDefaultError()
    {
        // arrange

        var bindingCtx = new Mock<ModelBindingContext>();
        bindingCtx
            .Setup(x => x.ModelName)
            .Returns("Test");

        var valueProvider = new Mock<IValueProvider>();

        bindingCtx
            .Setup(x => x.ValueProvider)
            .Returns(valueProvider.Object);

        var providerResult = new ValueProviderResult(new StringValues(new []{ "test"}));

        valueProvider
            .Setup(x => x.GetValue("Test"))
            .Returns(providerResult);

        var binder = new JsonModelBinder();

        // act

        await binder.BindModelAsync(bindingCtx.Object)
            .ConfigureAwait(false);

        // assert

        Assert.True(bindingCtx.Object.ModelState.ErrorCount > 0);
    }