判斷序列中的任何或所有項目是否全都符合條件

如果序列中所有的項目都符合條件，則 All 運算子會傳回 true。

如果序列中有任何項目符合條件，則 Any 運算子會傳回 true。

範例 1

下列範例會傳回至少有一張訂單的客戶序列。 如果指定的 Customer 有任何 Order，則 Where/where 子句會評估為 true。

var OrdersQuery =
    from cust in db.Customers
    where cust.Orders.Any()
    select cust;

Dim OrdersQuery = _
    From cust In db.Customers _
    Where cust.Orders.Any() _
    Select cust

範例 2

下列 Visual Basic 程式碼會判斷尚未下單的客戶清單，並且確保該清單中的每位客戶都有一個連絡人名稱。

Public Sub ContactsAvailable()
    Dim db As New Northwnd("c:\northwnd.mdf")
    Dim result = _
        (From cust In db.Customers _
         Where Not cust.Orders.Any() _
         Select cust).All(AddressOf ContactAvailable)

    If result Then
        Console.WriteLine _
    ("All of the customers who have made no orders have a contact name")
    Else
        Console.WriteLine _
    ("Some customers who have made no orders have no contact name")
    End If
End Sub

Function ContactAvailable(ByVal contact As Object) As Boolean
    Dim cust As Customer = CType(contact, Customer)
    Return (cust.ContactTitle Is Nothing OrElse _
        cust.ContactTitle.Trim().Length = 0)
End Function

範例 3

下列 C# 範例會傳回其訂單具有以 "C" 開頭之 ShipCity 的客戶序列。 傳回的資料中還包含了沒有訂單的客戶 (根據設計，All 運算子會針對空序列傳回 true。)使用 Count 運算子，可以在主控台輸出中排除沒有訂單的客戶。

var custEmpQuery =
    from cust in db.Customers
    where cust.Orders.All(o => o.ShipCity.StartsWith("C"))
    orderby cust.CustomerID
    select cust;

foreach (Customer custObj in custEmpQuery)
{
    if (custObj.Orders.Count > 0)
        Console.WriteLine("CustomerID: {0}", custObj.CustomerID);
    foreach (Order ordObj in custObj.Orders)
    {
        Console.WriteLine("\t OrderID: {0}; ShipCity: {1}",
            ordObj.OrderID, ordObj.ShipCity);
    }
}

另請參閱

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