无法更新 SharePoint 发布页面图像

Cannot Update SharePoint Publishing Page Image

我正在尝试更新发布页面图像 url 但在执行查询命令后不知何故。它的值保存为 null

        ClientContext targetContext = new ClientContext ("REAL URL");
        Microsoft.SharePoint.Client.File targetFile = targetContext.Web.GetFileByServerRelativeUrl ("REAL URL");
        var targetPublishingPage = PublishingPage.GetPublishingPage (targetContext, targetFile.ListItemAllFields);
        targetContext.Load (targetPublishingPage.ListItem);
        targetContext.ExecuteQuery ();
        targetFile.CheckOut ();
        targetPublishingPage.ListItem["PublishingPageImage"] = "REAL URL";
        targetPublishingPage.ListItem.Update ();
        targetContext.ExecuteQuery ();

发布图像字段值应按以下格式指定:<img src='{imageurl}'>

例子

using (var ctx = new ClientContext(webUri))
{
    var pageFile = ctx.Web.GetFileByServerRelativeUrl(pageUrl);
    var pageItem = pageFile.ListItemAllFields;
    pageItem["PublishingPageImage"] = "<img src='/PublishingImages/PageLogo.png'>";
    pageItem.Update();
    ctx.ExecuteQuery();
}