如何使用 SharePoint CSOM 获取文档预览图像 [英] How to get document preview image using SharePoint CSOM

问题描述

我想以编程方式从 SharePoint 检索文档的缩略图.我正在尝试做的是以下内容:

I would like to programmatically retrieve thumbnails of documents from SharePoint. What I'm trying to do is the following:

document.GetImagePreviewUrl(width, height, clientType);

这只是返回一个空的ClientResult.我不确定要输入什么作为 clientType 值.

This just returns an empty ClientResult. I am not sure what to enter as clientType value.

我也尝试使用 this 方法(通过使用 WebClient 并下载文件).但这只是返回一个 403 响应.

I have also tried to use this method programmatically (by using WebClient and downloading the file). But that just returns a 403 response.

我在这里看到的可能解决方案如下:

The possible solutions I see here are the following:

• 弄清楚要输入什么作为 clientType 并以这种方式检索预览网址.
• 弄清楚如何以编程方式告诉 SharePoint 我已获得授权(例如使用 WebClient 和标头).

• Figure out what to enter as clientType and retrieve the preview url that way.
• Figure out how to tell SharePoint that I am authorized programmatically (using WebClient and headers for instance).

关于这两个选项我确实需要一些帮助，我不知道从哪里开始，因为这两个选项都没有很好的记录.

I do need some help regarding these two options, I am not sure where to start since both options aren't well documented.

推荐答案

我想出了一个办法，403 错误是因为 sharepoint 不知道我是谁.经过一些研究和摆弄，我发现您发送到预览页面的请求包含一个身份验证 cookie.这个cookie可以通过使用这段代码的代码生成:

I've figured out a way to do it, the 403 error was caused because sharepoint had no idea who I was. After some research and fiddling I found out that the request you send to the preview page contains an authentication cookie. This cookie can be generated by code using this piece of code:

// Create an authentication cookie which we can send with the request so sharepoint knows who we are.
var authCookie = credentials.GetAuthenticationCookie(new Uri(imageUrl));
client.Headers.Add(HttpRequestHeader.Cookie, authCookie);
// Download the image data to a byte array
image = client.DownloadData(imageUrl);

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