Xamarin.Forms将图像上传到服务器目录

Question

我必须将我的应用程序中的图像上传到php web服务我试过这段代码：

private void  upload(MediaFile mediaFile)
{
    try
    {   
        byte[] data = ReadFully(mediaFile.Source);

        var imageStream = new ByteArrayContent(data);
        imageStream.Headers.ContentDisposition = new ContentDispositionHeaderValue("attachment")
        {
            FileName = Guid.NewGuid() + ".Png"
        };

        var multi = new MultipartContent();
        multi.Add(imageStream);
        var client = new System.Net.Http.HttpClient();
        client.BaseAddress = new Uri("url");
        var result = client.PostAsync("api/ManageImage", multi).Result;
    }
    catch (Exception e)
    {

    }

}

PHP：

<?php

    $uploads_dir = 'Image/'; //Directory to save the file that comes from 
    client application.      
    if ($_FILES["file"]["error"] == UPLOAD_ERR_OK)       
    {      
        $tmp_name = $_FILES["file"]["tmp_name"];     
        $name = $_FILES["file"]["name"];    
        move_uploaded_file($tmp_name, "$uploads_dir/$name");   
    }
?>

我使用Xam.Plugin.FilePicker获取文件，但我不知道如何发送以及如何重新获取图像