首先，在Web.config文件中添加Cloudinary账户信息：

然后安装Cloudinary官方NuGet包：

Install-Package Cloudinary -Version 1.2.0

在上传图片的Controller中，添加如下代码：

[HttpPost]
public async Task Upload()
{
    try
    {
        var httpRequest = HttpContext.Current.Request;

        if (httpRequest.Files.Count > 0)
        {
            var file = httpRequest.Files[0];
            var fileName = Path.GetFileName(file.FileName);
            var cloudinary = new Cloudinary(
                new Account(
                    ConfigurationManager.AppSettings["CloudinaryCloudName"],
                    ConfigurationManager.AppSettings["CloudinaryApiKey"],
                    ConfigurationManager.AppSettings["CloudinaryApiSecret"]));

            var uploadParams = new ImageUploadParams()
            {
                File = new FileDescription(fileName, file.InputStream)
            };

            var uploadResult = await cloudinary.UploadAsync(uploadParams);

            return Ok();
        }
    }
    catch (Exception ex)
    {
        return BadRequest(ex.Message);
    }

    return BadRequest();
}

其中，CloudinaryCloudName、CloudinaryApiKey和CloudinaryApiSecret需要替换为你自己的Cloudinary账户信息。