LINQ:
var temp = from p in db.jj_Credentials
group p by p.ProfessionID into g
select new
{
g.Key,
MaxPrice = g.Max(p => p.CredentialsRankID)
};
EF：
var temp1 = db.jj_Credentials.GroupBy(m => m.ProfessionID).Select(m => m.Max(o => o.CredentialsRankID));
foreach(var p in temp1)
{
Response.Write(p);
}
补充：取最大值后取得当前完整记录的方法，两种写法：
写法1
//写法1
var list1 = db.jj_Credentials.Where(m => m.UserId == UserContext.UserID && m.IsAudit).OrderByDescending(m => m.CredentialsRankID).ToList().GroupBy(x => x.ProfessionID)
.SelectMany(t => t.Select((b, i) => new { b, i }).Where(m => m.i == )).Select(m => m.b); foreach (var i in list1)
{
Response.Write(string.Format("{0} {1} {2} {3}<br>", i.CredentialsID, i.UserId, i.CredentialsRankID, i.ProfessionID));
}
写法2
//写法2
var list = db.jj_Credentials.Where(m => m.UserId == UserContext.UserID && m.IsAudit).OrderByDescending(x => x.CredentialsRankID).ToList().GroupBy(x => x.ProfessionID)
.Select(g => new { g, count = g.Count() })
.SelectMany(t => t.g.Select(b => b).Zip(Enumerable.Range(, t.count), (j, i) =>
new
{
CredentialsID = j.CredentialsID,
UserID = j.UserId,
CredentialsRankID = j.CredentialsRankID,
ProfessionID = j.ProfessionID,
rn = i
}).Where(x => x.rn == )); //打印
foreach (var i in list)
{
Response.Write(string.Format("{0} {1} {2} {3}<br>", i.CredentialsID, i.UserID, i.CredentialsRankID, i.ProfessionID));
}