'Exception has been thrown by the target of an invocation' during export of webpart for user subsite

Question

I have one subsite under a user site, which have one wiki page(at least 2,3 versions) with multiple web parts in it.
(To create sub site under subsite:

1. Go to user site "https://<tenantname>-my.sharepoint.com/personal/<useremailfirstpart>_<tenantname>_onmicrosoft_com"
   for ex. https://bd4-my.sharepoint.com/personal/PaleD_bd4_onmicrosoft_com/Documents/Forms/All.aspx
   user email: PaleD@onmicrosoft.com
2. Go to site contents from setting option(if not visible view in classic mode)
3. From site content new option we can create sub site using normal flow.)

Create a wiki page add a web part and publish it. then open page in edit mode and add web part republish again. do this again so file will have 3 versions.

Now when we try to export the web part using below code we get error "Exception has been thrown by the target of an invocation".

// main site url:"https://<tenant>.sharepoint.com/sites/TestSite06";  
// sub site url:"https://<tenant>.sharepoint.com/sites/TestSite06/SubSite01";  
  
var siteCollectionUrl = "https://<tenant>.sharepoint.com/sites/TestSite06"; // Main site  
  
using (ClientContext clientcontext = new ClientContext(siteCollectionUrl))  
{	  
	clientcontext.Credentials = new SharePointOnlineCredentials("username", "password with secure string");  
  
	Web site = clientcontext.Site.OpenWebById(new Guid("f507b7e6-eaee-407d-b56c-05e0aeb2a994")); // open web with subsite id  
	List list = site.Lists.GetById(new Guid("98ef5374-0168-4e33-9a96-56ec0b1c3e44")); // Get site pages using ID from subsite  
	var listItem = list.GetItemByUniqueId(new Guid("1a439e3d-73a6-4ba3-8ea7-b77963aa07b2")); // Get wiki page with Webparts using ID  
	clientcontext.Load(listItem);  
	clientcontext.Load(listItem.File);  
	clientcontext.ExecuteQuery();  
  
	Dictionary<string, string> backupWebparts = new Dictionary<string, string>();  
  
	//Load webparts if any  
	LimitedWebPartManager webPartManager = listItem.File.GetLimitedWebPartManager(PersonalizationScope.Shared);  
	clientcontext.Load(webPartManager.WebParts, wpd => wpd.Include(wp => wp.Id, wp => wp.ZoneId, wp => wp.WebPart));  
  
	clientcontext.ExecuteQuery();  
  
	//Check is webparts instanciated properly and it contains web parts  
	if (null != webPartManager && webPartManager.IsObjectPropertyInstantiated(nameof(webPartManager.WebParts))  
		&& webPartManager.WebParts.AreItemsAvailable && webPartManager.WebParts.Count > 0)  
	{  
		var file = listItem.File;  
  
		foreach (var webPartDef in webPartManager.WebParts)  
		{  
			bool changedExportMode = false;  
			var exportMode = webPartDef.WebPart.ExportMode;  
  
			//Change export mode to all if it is none, as none mode does not allow webpart to export its xml  
			if (webPartDef.WebPart.ExportMode == WebPartExportMode.None)  
			{  
				//when we are changing the export mode, automatically it is checking in file with minor version  
				//to stop creating minor version check in of file, check out the file before doing changes and perform undocheckout after changes  
				//which will not create any minor version check in  
				file.CheckOut();  
  
				webPartDef.OpenWebPart();  
				webPartDef.WebPart.ExportMode = WebPartExportMode.All;  
				webPartDef.SaveWebPartChanges();  
  
				changedExportMode = true;  
			}  
  
			//Getting web part xml  
			var webpartXMLRes = webPartManager.ExportWebPart(webPartDef.Id);  
  
			//Resetting the export mode of webpart to its original value                              
			if (changedExportMode)  
			{  
				//Setting original export mode so that original value should get backed up  
				webPartDef.WebPart.ExportMode = exportMode;  
  
				//discard the checkout as we have checked out earlier  
				file.UndoCheckOut();  
			}  
  
			clientcontext.ExecuteQuery();  
  
			//Adding webpart into backup, after resetting export mode to its original value  
			backupWebparts.Add(webPartDef.Id.ToString(), webpartXMLRes.Value);  
		}  
	}  
  
}  

Please someone help. Thanks in advance !

@RaytheonXie_MSFT
@Tong Zhang_MSFT

Answer 1

Hi @Yuvraj Patil ,

Based on the code you provided, I cannot reproduce your problem, in my test, there is an error in this sentence : var webPartDef=webPartManager.WebParts[0]; . As a workaround, I recommend you can refer to the following code to export SharePoint Webpart using CSOM:

var limitedWebPartManager = file.GetLimitedWebPartManager(PersonalizationScope.Shared);  
            var webPartDefinitons = limitedWebPartManager.WebParts;  
            clientcontext.Load(webPartDefinitons);  
            clientcontext.ExecuteQuery();  
            foreach (var webpartDefintion in webPartDefinitons)  
            {  
                try  
                {  
                    var webPartId = webpartDefintion.Id;  
                    var webPartXML = limitedWebPartManager.ExportWebPart(webPartId);  
                    clientcontext.ExecuteQuery();  
                    clientcontext.Load(webpartDefintion, def => def.ZoneId, def => def.Id);  
                    clientcontext.ExecuteQuery();  
  
                }  
                catch (Exception exception)  
                {  
                    Console.WriteLine(exception);  
                }  
            }  

More information for reference: Export SharePoint Webpart using csom

Hope it can help you. Thanks for your understanding.

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