[SOLVED] Form key or value length limit 2048 exceeded

Issue

I am using asp.net core to build API. I have a request that allow user to upload profile image using this code

 [HttpPost("{company_id}/updateLogo")]
        public async Task<IActionResult> updateCompanyLogo(IFormFile imgfile,int company_id)
        {
            string imageName;
            // upload file
            if (imgfile == null || imgfile.Length == 0)
                imageName = "default-logo.jpg";
            else
            {
                imageName = Guid.NewGuid() + imgfile.FileName;
                var path = _hostingEnvironment.WebRootPath + [email protected]"\Imgs\{imageName}";
                if (imgfile.ContentType.ToLower().Contains("image"))
                {
                    using (var fileStream = new FileStream(path, FileMode.Create))
                    {
                        await imgfile.CopyToAsync(fileStream);
                    }
                }
            }
.
.

but it keeps returning this exception: Form key or value length limit 2048 exceeded
The Request
http://i.imgur.com/25B0qkD.png

Update:
I have tried this code but it doesn’t work

    services.Configure<FormOptions>(options =>
    {
        options.ValueLengthLimit = int.MaxValue; //not recommended value
        options.MultipartBodyLengthLimit = long.MaxValue; //not recommended value
    });

Solution

By default, ASP.NET Core enforces key/value length limit of 2048 inside FormReader as constant and applied in FormOptions as shown below:

public class FormReader : IDisposable
{
    public const int DefaultValueCountLimit = 1024;
    public const int DefaultKeyLengthLimit = 1024 * 2; // 2048
    public const int DefaultValueLengthLimit = 1024 * 1024 * 4; // 4194304
    // other stuff
}

public class FormOptions
{
    // other stuff
    public int ValueCountLimit { get; set; } = DefaultValueCountLimit;
    public int KeyLengthLimit { get; set; } = FormReader.DefaultKeyLengthLimit;
    public int ValueLengthLimit { get; set; } = DefaultValueLengthLimit;
    // other stuff
}

Hence, you may create a custom attribute to explicitly set key/value length limit on your own by using KeyValueLimit and ValueCountLimit property (also ValueLengthLimit etc.):

[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class RequestSizeLimitAttribute : Attribute, IAuthorizationFilter, IOrderedFilter
{
    private readonly FormOptions _formOptions;

    public RequestSizeLimitAttribute(int valueCountLimit)
    {
        _formOptions = new FormOptions()
        {
            // tip: you can use different arguments to set each properties instead of single argument
            KeyLengthLimit = valueCountLimit,
            ValueCountLimit = valueCountLimit,
            ValueLengthLimit = valueCountLimit

            // uncomment this line below if you want to set multipart body limit too
            // MultipartBodyLengthLimit = valueCountLimit
        };
    }

    public int Order { get; set; }

    // taken from /a/38396065
    public void OnAuthorization(AuthorizationFilterContext context)
    {
        var contextFeatures = context.HttpContext.Features;
        var formFeature = contextFeatures.Get<IFormFeature>();

        if (formFeature == null || formFeature.Form == null)
        {
            // Setting length limit when the form request is not yet being read
            contextFeatures.Set<IFormFeature>(new FormFeature(context.HttpContext.Request, _formOptions));
        }
    }
}

Usage example in action method:

[HttpPost("{company_id}/updateLogo")]
[RequestSizeLimit(valueCountLimit: 2147483648)] // e.g. 2 GB request limit
public async Task<IActionResult> updateCompanyLogo(IFormFile imgfile, int company_id)
{
    // contents removed for brevity
}

NB: If latest version of ASP.NET Core is being used, change property named ValueCountLimit to KeyCountLimit.

Update: The Order property must be included on attribute class because it is a member of implemented interface IOrderedFilter.

Similar issues:

Form submit resulting in "InvalidDataException: Form value count limit 1024 exceeded."

Request.Form throws exception

Answered By – Tetsuya Yamamoto

Answer Checked By – Senaida (BugsFixing Volunteer)

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