Unexpected end of Stream, the content may have already been read by another component. Microsoft.AspNetCore.WebUtilities.MultipartReaderStream

In asp.net core 3, You have to add factories.RemoveType<FormFileValueProviderFactory>(); to your DisableFormValueModelBindingAttribute attribute.

Code

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class DisableFormValueModelBindingAttribute : Attribute, IResourceFilter
{
    public void OnResourceExecuting(ResourceExecutingContext context)
    {
        var factories = context.ValueProviderFactories;
        factories.RemoveType<FormValueProviderFactory>();
        factories.RemoveType<FormFileValueProviderFactory>();
        factories.RemoveType<JQueryFormValueProviderFactory>();
    }

    public void OnResourceExecuted(ResourceExecutedContext context)
    {
    }
}

Documentation

It turns out that I had to disable form value model binding by using the attribute below.

[HttpPost]
    [Route("")]
    [DisableFormValueModelBinding]
    public async Task<IActionResult> Post()

The attribute implementation is below

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method)]
public class DisableFormValueModelBindingAttribute : Attribute, IResourceFilter
{
    public void OnResourceExecuting(ResourceExecutingContext context)
    {
        var factories = context.ValueProviderFactories;
        factories.RemoveType<FormValueProviderFactory>();
        factories.RemoveType<JQueryFormValueProviderFactory>();
    }

    public void OnResourceExecuted(ResourceExecutedContext context)
    {
    }
}