第一步：

var userids = entityPairs.Select(p => p.Item1.OwnerId).ToList();            var userMapping = (context.Set
     
      ()                .Where(u => userids.Contains(u.Id))                .Select(u => new {                    id = u.Id,                    username = u.Username,                    nickname = u.Nickname,                }).ToDictionary(u => u.id, u => u));
     

 

第二步：

pair.Item2["Username"] = userMapping.GetOrDefault((long)pair.Item1.OwnerId).nickname;

示列代码一：管理员获取

/// 
        /// 选择需要的字段        /// 
        [Tested("Common.Test.Admin.AdminAdminsControllerTest")]        public void Select(EntireDbContext context,            IList
     
      
       >> entityPairs) {            // 获取关联的用户和角色名称            var adminIds = entityPairs.Select(p => p.Item1.Id).ToList();            var userMapping = (context.Set
       
        ()                .Where(u => adminIds.Contains(u.Id))                .Select(u => new {                    id = u.Id,                    username = u.Username,                    nickname = u.Nickname,                    roleId = u.RoleId,                    roleName = u.Role.Name // 这里会转换成join                }).ToDictionary(u => u.id, u => u));            foreach (var pair in entityPairs) {                pair.Item2["Id"] = pair.Item1.Id;                pair.Item2["SuperAdmin"] = (                    pair.Item1.SuperAdmin ? BooleanValues.True : BooleanValues.Null);                pair.Item2["CreateTime"] = pair.Item1.CreateTime.ToClientTimeString();                pair.Item2["Username"] = userMapping.GetOrDefault(pair.Item1.Id)?.username;                pair.Item2["Nickname"] = userMapping.GetOrDefault(pair.Item1.Id)?.nickname;                pair.Item2["RoleName"] = userMapping.GetOrDefault(pair.Item1.Id)?.roleName;                pair.Item2["RoleId"] = userMapping.GetOrDefault(pair.Item1.Id)?.roleId;            }        }