/// <summary>
        /// 执行请求前
        /// </summary>
        /// <param name="context">上下文</param>
        /// <param name="parameter">特性关联的参数</param>
        async Task IApiParameterable.BeforeRequestAsync(ApiActionContext context, ApiParameterDescriptor parameter)
        {
            var httpContent = context.EnsureNoGet().RequestMessage.Content.CastOrCreateMultipartContent();

            httpContent.AddFile(this.GetStream(), parameter.Name, this.FileName, this.ContentType);
            context.RequestMessage.Content = httpContent;
            await TaskExtend.CompletedTask;
        }
        /// <summary>
        /// http请求之前
        /// </summary>
        /// <param name="context">上下文</param>
        /// <param name="parameter">特性关联的参数</param>
        /// <returns></returns>
        async Task IApiParameterable.BeforeRequestAsync(ApiActionContext context, ApiParameterDescriptor parameter)
        {
            var keyValue    = new KeyValuePair <string, string>(parameter.Name, this.stringValue);
            var httpContent = await context.EnsureNoGet().RequestMessage.Content.MergeKeyValuesAsync(new[] { keyValue });

            context.RequestMessage.Content = httpContent;

            await TaskExtend.CompletedTask;
        }