public async Task TestAggregateFunc()
{
var dr = await CreateDriver();
var d = await dr.From <MyModel>()
.Select(x => AggregateFunc.Max(x.Id))
.ToSingleAsync();
Assert.Equal(3, d);
}
public void FuncAggregateMaxMin()
{
var q1 = Builders <MyModel> .Select(x => AggregateFunc.Max(x.Id)).Where(x => x.DateTime > Func.Now());
Utils.AssertRawQuery(q1, @"SELECT MAX(""id"") FROM model WHERE (datetime) > (NOW())");
var q2 = Builders <MyModel> .Select(x => AggregateFunc.Min(x.Id)).Where(x => x.DateTime > Func.Now());
Utils.AssertRawQuery(q2, @"SELECT MIN(""id"") FROM model WHERE (datetime) > (NOW())");
}
public void FuncAggregateSum()
{
var q1 = Builders <MyModel> .Select(x => AggregateFunc.Sum(x.ValFloat));
Utils.AssertRawQuery(q1, @"SELECT SUM(val_f32) FROM model");
}
/// <summary>
/// 查询极值
/// </summary>
/// <typeparam name="C">极值的类型</typeparam>
/// <param name="predicate">查询条件</param>
/// <param name="selector">返回值</param>
/// <param name="aggregateFunc">返回的极值，极大值、极小值</param>
/// <returns>返回极值</returns>
public C FindExtreProp <C>(Expression <Func <TEntity, bool> > predicate, Expression <Func <TEntity, C> > selector, AggregateFunc aggregateFunc)
{
using (DbContext dbContext = CreateDbContext())
{
IQueryable <TEntity> query = dbContext.Set <TEntity>().AsNoTracking().Where(predicate);
if (aggregateFunc == AggregateFunc.MAX)
{
return(query.Max(selector));
}
else if (aggregateFunc == AggregateFunc.MIN)
{
return(query.Min(selector));
}
else
{
throw new Exception("枚举只能使用MAX、MIN");
}
}
}
