SP2013 Adding custom webpart(sandbox) to a page programmatically using CSOM

I'm trying to add a webpart(sandboxed) to a page programmatically using CSOM.

I've created a simple windows forms application and tried the below, it gives me error

A first chance exception of type 'Microsoft.SharePoint.Client.ServerException' occurred in Microsoft.SharePoint.Client.Runtime.dll"- Server Exception occurred. Additional Information: Cannot Import this webpart

using (ClientContext context = new ClientContext("URL"))
        {
            Web web = context.Web;
            File file = web.GetFileByServerRelativeUrl("/SitePages/Test.aspx");
            LimitedWebPartManager wpMgr = file.GetLimitedWebPartManager(PersonalizationScope.Shared);
    string webpartxml = "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                            "<webParts>" +
                "<webPart xmlns='http://ift.tt/1fI5tWY'>" +
                "<metaData>" +
                    "<type name=\"CustomVisualWebPartProject.VisualWebPart1.VisualWebPart1, CustomVisualWebPartProject, Version=1.0.0.0, Culture=neutral, PublicKeyToken=28942db35e131a1c\" />" +
                "<importErrorMessage>Cannot Import this webpart</importErrorMessage>" +
                    "</metaData>"+
                "<data>"+
                    "<properties>"+
                    "<property name=\"Title\" type=\"string\">CustomVisualWebPartProject - VisualWebPart1</property> "+
                    "<property name=\"Description\" type=\"string\">My Visual Web Part</property>" +
                    "<property name=\"ChromeType\" type=\"chrometype\">None</property>" +
                    "</properties>" +
                "</data>" +
                "</webPart></webParts>";
            WebPartDefinition webPartDef = wpMgr.ImportWebPart(webpartxml);
            wpMgr.AddWebPart(webPartDef.WebPart, "Left", 1);
            context.ExecuteQuery();
    }

Please let me know how to fix this error.