SharePoint 客户端对象模型共用ClientContext的坑

private static void Main(string[] args)
{
	Test2();
}

private static void Test2()
{
	var clientContext = CreateClientContext();
	var oList = clientContext.Web.Lists.GetByTitle("title");
	var title = "xxxxxx";
	var email = "abc@qq.com";

	var itemCreateInfo = new ListItemCreationInformation();
	var oListItem = oList.AddItem(itemCreateInfo);
	oListItem["Title"] = title;
	//两个方法的坑
	oListItem["Email"] = GetUserIdByEmail(email); //GetUserIdByEmail(clientContext, email);

	oListItem.Update();
	clientContext.ExecuteQuery();
}

private static int GetUserIdByEmail(string email)
{
	using (var ctx = CreateClientContext())
	{
		var result = Utility.ResolvePrincipal(ctx, ctx.Web, email, PrincipalType.User,
			PrincipalSource.All, null, true);

		ctx.ExecuteQuery();
		if (result != null)
		{
			var user = ctx.Web.EnsureUser(result.Value.LoginName);
			ctx.Load(user);
			ctx.ExecuteQuery();
			return user != null ? user.Id : -1;
		}
	}
	return -1;
}
//错误的方法
private static int GetUserIdByEmail(ClientContext ctx, string email)
{
	var result = Utility.ResolvePrincipal(ctx, ctx.Web, email, PrincipalType.User,
		PrincipalSource.All, null, true);
	ctx.ExecuteQuery();
	if (result != null)
	{
		var user = ctx.Web.EnsureUser(result.Value.LoginName);
		ctx.Load(user);
		ctx.ExecuteQuery();
		return user != null ? user.Id : -1;
	}
	return -1;
}

private static ClientContext CreateClientContext()
{
	var clientContext = new ClientContext("site url")
	{
		Credentials = new NetworkCredential("_userName", "_password", "_domainName")
	};
	return clientContext;
}