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;

}