如何：查找数值序列中的最大值 (LINQ to SQL)

更新：November 2007

使用 Max 运算符可查找数值序列中的最高值。

示例

下面的示例查找任何员工的最近雇佣日期。

如果您对 Northwind 示例数据库运行此查询，则输出为：11/15/1994 12:00:00 AM。

Dim latestHireDate = Aggregate emp In db.Employees _
                     Into Max(emp.HireDate)

Console.WriteLine(latestHireDate)

System.Nullable<DateTime> latestHireDate =
    (from emp in db.Employees
    select emp.HireDate)
    .Max();

Console.WriteLine(latestHireDate);

下面的示例查找任何产品的最大库存件数。

如果您对 Northwind 示例数据库运行此示例，则输出为：125。

Dim maxUnitsInStock = Aggregate prod In db.Products _
                      Into Max(prod.UnitsInStock)

Console.WriteLine(maxUnitsInStock)

System.Nullable<Int16> maxUnitsInStock =
    (from prod in db.Products
    select prod.UnitsInStock)
    .Max();

Console.WriteLine(maxUnitsInStock);

下面的示例使用 Max 查找每个类别中单价最高的 Products。然后，按类别列出输出结果。

Dim maxQuery = From prod In db.Products() _
    Group prod By prod.CategoryID Into grouping = Group _
    Select CategoryID, _
    MostExpensiveProducts = _
        (From prod2 In grouping _
        Where prod2.UnitPrice = _
        grouping.Max(Function(prod3) prod3.UnitPrice))

For Each grp In maxQuery
    Console.WriteLine(grp.CategoryID)
    For Each listing In grp.MostExpensiveProducts
        Console.WriteLine(listing.ProductName)
    Next
Next

var maxQuery =
    from prod in db.Products
    group prod by prod.CategoryID into grouping
    select new
    {
        grouping.Key,
        MostExpensiveProducts =
            from prod2 in grouping
            where prod2.UnitPrice == grouping.Max(prod3 =>
                prod3.UnitPrice)
            select prod2
    };

foreach (var grp in maxQuery)
{
    Console.WriteLine(grp.Key);
    foreach (var listing in grp.MostExpensiveProducts)
    {
        Console.WriteLine(listing.ProductName);
    }
}

如果您对 Northwind 示例数据库运行上一个查询，所得到的结果将与如下内容类似：

1

Côte de Blaye

2

Vegie-spread

3

Sir Rodney's Marmalade

4

Raclette Courdavault

5

Gnocchi di nonna Alice

6

Thüringer Rostbratwurst

7

Manjimup Dried Apples

8

Carnarvon Tigers

请参见

概念

下载示例数据库 (LINQ to SQL)

其他资源

聚合查询 (LINQ to SQL)