convertir un IFormFile en Cadena de Json

static async Task<string> ConvertIFormFileToString(IFormFile file)
{
    var result = new StringBuilder();
    using (var reader = new StreamReader(file.OpenReadStream()))
    {
        while (reader.Peek() >= 0)
            result.AppendLine(await reader.ReadLineAsync());
    }

    return result.ToString();
}