/// <summary>
/// 当给定的用户不存在时，向数据源添加用户。返回用户实体对象。
/// </summary>
/// <param name="dataFacade">数据源外观。</param>
/// <param name="wechatId">用户的微信 ID。</param>
/// <returns></returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="dataFacade"/> 为 null
/// 或
/// <paramref name="wechatId"/> 为 null
/// </exception>
public static async Task <UserEntity> AddOrFindUserByWechatId(this IDataFacade dataFacade, string wechatId)
{
if (dataFacade == null)
{
throw new ArgumentNullException(nameof(dataFacade));
}
if (wechatId == null)
{
throw new ArgumentNullException(nameof(wechatId));
}
var existingEntity = await dataFacade.Users
.Where(u => u.WechatId == wechatId)
.FirstOrDefaultAsync();
if (existingEntity != null)
{
// 用户已经存在于数据源中
return(existingEntity);
}
// 用户在数据源中未找到
var userEntity = new UserEntity
{
WechatId = wechatId
};
try
{
dataFacade.AddUser(userEntity);
await dataFacade.CommitChanges();
return(userEntity);
}
catch (DataFacadeException)
{
// 重做用户查询
existingEntity = await dataFacade.Users
.Where(u => u.WechatId == wechatId)
.FirstOrDefaultAsync();
if (existingEntity != null)
{
return(existingEntity);
}
// 重做用户查询仍然无法找到用户
throw;
}
}