如何处理 AspNet Core 自定义 ModelBinder 中的错误

Question

I´m trying to create a custom model binder that cancels the request when the given data is invalid.

public sealed class DeploymentIdModelBinder : IModelBinder
{
    public Task BindModelAsync(ModelBindingContext bindingContext)
    {
        string modelName = bindingContext.ModelName;

        string? value = bindingContext
            .ValueProvider
            .GetValue(modelName)
            .FirstValue;

        if (value is null)
            return Task.CompletedTask;

        if(DeploymentId.TryParse(value, out var id))
        {
            bindingContext.Result = ModelBindingResult.Success(id);
        }
        else
        {
            bindingContext.ModelState.TryAddModelError(modelName, $"{value} is not a valid {nameof(DeploymentId)}.");
            bindingContext.Result = ModelBindingResult.Failed();
        }
        return Task.CompletedTask;
    }
}

[HttpGet]
[Route("download/{deploymentId}")]
public async Task<IActionResult> DownloadDeployment(DeploymentId deploymentId)
{
    ...
}

I expected to not hit the endpoint if I pass in an invalid DeploymentId. But instead the method gets called with deploymentId = null .

Do I have a wrong expectation/Do I missunderstand how the binders should work? And if, how would I do it the wright way?

Thanks for your answers!

Answer 1

You can refer to this document . And use url like: https://localhost:7273/authors/index?id=1

result: