json-serialization-3.cs

public class FormEntryDtoModelBinder : IModelBinder
{
    public async Task BindModelAsync(ModelBindingContext bindingContext)
    {
        if (bindingContext == null)
        {
            throw new ArgumentNullException(nameof(bindingContext));
        }

        using (var reader = new StreamReader(bindingContext.HttpContext.Request.Body))
        {
            var body = await reader.ReadToEndAsync().ConfigureAwait(continueOnCapturedContext: false);

            FormEntryDto? value = JsonSerializer.Deserialize<FormEntryDto>(body);
            if (value != null)
            {
                bindingContext.Result = ModelBindingResult.Success(value);
            }
        }
    }
}