List<T>.Insert(Int32, T) Metodo

Riferimento

Definizione

Spazio dei nomi:: System.Collections.Generic

Assembly:: System.Collections.dll

Assembly:: mscorlib.dll

Assembly:: netstandard.dll

Origine:: List.cs

Origine:: List.cs

Origine:: List.cs

Importante

Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.

Inserisce un elemento in List<T> in corrispondenza dell'indice specificato.

public:
 virtual void Insert(int index, T item);

public void Insert (int index, T item);

abstract member Insert : int * 'T -> unit
override this.Insert : int * 'T -> unit

Public Sub Insert (index As Integer, item As T)

Parametri

index: Int32

Indice in base zero nel quale item deve essere inserito.

item: T

Oggetto da inserire. Il valore può essere null per i tipi di riferimento.

Implementazioni

Insert(Int32, T)

Eccezioni

ArgumentOutOfRangeException

index è minore di 0.

-oppure-

index è maggiore di Count.

Esempio

Nell'esempio seguente viene illustrato come aggiungere, rimuovere e inserire un semplice oggetto business in un oggetto List<T>.

using System;
using System.Collections.Generic;
// Simple business object. A PartId is used to identify the type of part
// but the part name can change.
public class Part : IEquatable<Part>
    {
        public string PartName { get; set; }

        public int PartId { get; set; }

        public override string ToString()
        {
            return "ID: " + PartId + "   Name: " + PartName;
        }
        public override bool Equals(object obj)
        {
            if (obj == null) return false;
            Part objAsPart = obj as Part;
            if (objAsPart == null) return false;
            else return Equals(objAsPart);
        }
        public override int GetHashCode()
        {
            return PartId;
        }
        public bool Equals(Part other)
        {
            if (other == null) return false;
            return (this.PartId.Equals(other.PartId));
        }
    // Should also override == and != operators.
    }
public class Example
{
    public static void Main()
    {
        // Create a list of parts.
        List<Part> parts = new List<Part>();

        // Add parts to the list.
        parts.Add(new Part() { PartName = "crank arm", PartId = 1234 });
        parts.Add(new Part() { PartName = "chain ring", PartId = 1334 });
        parts.Add(new Part() { PartName = "regular seat", PartId = 1434 });
        parts.Add(new Part() { PartName = "banana seat", PartId = 1444 });
        parts.Add(new Part() { PartName = "cassette", PartId = 1534 });
        parts.Add(new Part() { PartName = "shift lever", PartId = 1634 });

        // Write out the parts in the list. This will call the overridden ToString method
        // in the Part class.
        Console.WriteLine();
        foreach (Part aPart in parts)
        {
            Console.WriteLine(aPart);
        }

        // Check the list for part #1734. This calls the IEquatable.Equals method
        // of the Part class, which checks the PartId for equality.
        Console.WriteLine("\nContains(\"1734\"): {0}",
        parts.Contains(new Part { PartId = 1734, PartName = "" }));

        // Insert a new item at position 2.
        Console.WriteLine("\nInsert(2, \"1834\")");
        parts.Insert(2, new Part() { PartName = "brake lever", PartId = 1834 });

        //Console.WriteLine();
        foreach (Part aPart in parts)
        {
            Console.WriteLine(aPart);
        }

        Console.WriteLine("\nParts[3]: {0}", parts[3]);

        Console.WriteLine("\nRemove(\"1534\")");

        // This will remove part 1534 even though the PartName is different,
        // because the Equals method only checks PartId for equality.
        parts.Remove(new Part() { PartId = 1534, PartName = "cogs" });

        Console.WriteLine();
        foreach (Part aPart in parts)
        {
            Console.WriteLine(aPart);
        }
        Console.WriteLine("\nRemoveAt(3)");
        // This will remove the part at index 3.
        parts.RemoveAt(3);

        Console.WriteLine();
        foreach (Part aPart in parts)
        {
            Console.WriteLine(aPart);
        }

            /*

             ID: 1234   Name: crank arm
             ID: 1334   Name: chain ring
             ID: 1434   Name: regular seat
             ID: 1444   Name: banana seat
             ID: 1534   Name: cassette
             ID: 1634   Name: shift lever

             Contains("1734"): False

             Insert(2, "1834")
             ID: 1234   Name: crank arm
             ID: 1334   Name: chain ring
             ID: 1834   Name: brake lever
             ID: 1434   Name: regular seat
             ID: 1444   Name: banana seat
             ID: 1534   Name: cassette
             ID: 1634   Name: shift lever

             Parts[3]: ID: 1434   Name: regular seat

             Remove("1534")

             ID: 1234   Name: crank arm
             ID: 1334   Name: chain ring
             ID: 1834   Name: brake lever
             ID: 1434   Name: regular seat
             ID: 1444   Name: banana seat
             ID: 1634   Name: shift lever

             RemoveAt(3)

             ID: 1234   Name: crank arm
             ID: 1334   Name: chain ring
             ID: 1834   Name: brake lever
             ID: 1444   Name: banana seat
             ID: 1634   Name: shift lever


         */
    }
}

Imports System.Collections.Generic

' Simple business object. A PartId is used to identify the type of part 
' but the part name can change. 
Public Class Part
    Implements IEquatable(Of Part)
    Public Property PartName() As String
        Get
            Return m_PartName
        End Get
        Set(value As String)
            m_PartName = Value
        End Set
    End Property
    Private m_PartName As String

    Public Property PartId() As Integer
        Get
            Return m_PartId
        End Get
        Set(value As Integer)
            m_PartId = Value
        End Set
    End Property
    Private m_PartId As Integer

    Public Overrides Function ToString() As String
        Return "ID: " & PartId & "   Name: " & PartName
    End Function
    Public Overrides Function Equals(obj As Object) As Boolean
        If obj Is Nothing Then
            Return False
        End If
        Dim objAsPart As Part = TryCast(obj, Part)
        If objAsPart Is Nothing Then
            Return False
        Else
            Return Equals(objAsPart)
        End If
    End Function
    Public Overrides Function GetHashCode() As Integer
        Return PartId
    End Function
    Public Overloads Function Equals(other As Part) As Boolean _
        Implements IEquatable(Of Part).Equals
        If other Is Nothing Then
            Return False
        End If
        Return (Me.PartId.Equals(other.PartId))
    End Function
    ' Should also override == and != operators.

End Class
Public Class Example
    Public Shared Sub Main()
        ' Create a list of parts.
        Dim parts As New List(Of Part)()

        ' Add parts to the list.
        parts.Add(New Part() With { _
             .PartName = "crank arm", _
             .PartId = 1234 _
        })
        parts.Add(New Part() With { _
             .PartName = "chain ring", _
             .PartId = 1334 _
        })
        parts.Add(New Part() With { _
             .PartName = "regular seat", _
             .PartId = 1434 _
        })
        parts.Add(New Part() With { _
             .PartName = "banana seat", _
             .PartId = 1444 _
        })
        parts.Add(New Part() With { _
             .PartName = "cassette", _
             .PartId = 1534 _
        })
        parts.Add(New Part() With { _
             .PartName = "shift lever", _
             .PartId = 1634 _
        })



        ' Write out the parts in the list. This will call the overridden ToString method
        ' in the Part class.
        Console.WriteLine()
        For Each aPart As Part In parts
            Console.WriteLine(aPart)
        Next


        ' Check the list for part #1734. This calls the IEquatable.Equals method
        ' of the Part class, which checks the PartId for equality.
        Console.WriteLine(vbLf & "Contains(""1734""): {0}", parts.Contains(New Part() With { _
             .PartId = 1734, _
             .PartName = "" _
        }))

        ' Insert a new item at position 2.
        Console.WriteLine(vbLf & "Insert(2, ""1834"")")
        parts.Insert(2, New Part() With { _
             .PartName = "brake lever", _
             .PartId = 1834 _
        })


        'Console.WriteLine();
        For Each aPart As Part In parts
            Console.WriteLine(aPart)
        Next

        Console.WriteLine(vbLf & "Parts[3]: {0}", parts(3))

        Console.WriteLine(vbLf & "Remove(""1534"")")

        ' This will remove part 1534 even though the PartName is different,
        ' because the Equals method only checks PartId for equality.
        parts.Remove(New Part() With { _
             .PartId = 1534, _
             .PartName = "cogs" _
        })

        Console.WriteLine()
        For Each aPart As Part In parts
            Console.WriteLine(aPart)
        Next

        Console.WriteLine(vbLf & "RemoveAt(3)")
        ' This will remove part at index 3.
        parts.RemoveAt(3)

        Console.WriteLine()
        For Each aPart As Part In parts
            Console.WriteLine(aPart)
        Next
    End Sub
    '
    '        This example code produces the following output:
    '        ID: 1234   Name: crank arm
    '        ID: 1334   Name: chain ring
    '        ID: 1434   Name: regular seat
    '        ID: 1444   Name: banana seat
    '        ID: 1534   Name: cassette
    '        ID: 1634   Name: shift lever
    '
    '        Contains("1734"): False
    '
    '        Insert(2, "1834")
    '        ID: 1234   Name: crank arm
    '        ID: 1334   Name: chain ring
    '        ID: 1834   Name: brake lever
    '        ID: 1434   Name: regular seat
    '        ID: 1444   Name: banana seat
    '        ID: 1534   Name: cassette
    '        ID: 1634   Name: shift lever
    '
    '        Parts[3]: ID: 1434   Name: regular seat
    '
    '        Remove("1534")
    '
    '        ID: 1234   Name: crank arm
    '        ID: 1334   Name: chain ring
    '        ID: 1834   Name: brake lever
    '        ID: 1434   Name: regular seat
    '        ID: 1444   Name: banana seat
    '        ID: 1634   Name: shift lever
    '   '
    '        RemoveAt(3)
    '
    '        ID: 1234   Name: crank arm
    '        ID: 1334   Name: chain ring
    '        ID: 1834   Name: brake lever
    '        ID: 1444   Name: banana seat
    '        ID: 1634   Name: shift lever
    '        

End Class


// Simple business object. A PartId is used to identify the type of part  
// but the part name can change.  
[<CustomEquality; NoComparison>]
type Part = { PartId : int ; mutable PartName : string } with
    override this.GetHashCode() = hash this.PartId
    override this.Equals(other) =
        match other with
        | :? Part as p -> this.PartId = p.PartId
        | _ -> false
    override this.ToString() = sprintf "ID: %i   Name: %s" this.PartId this.PartName

[<EntryPoint>]
let main argv = 
    // We refer to System.Collections.Generic.List<'T> by its type 
    // abbreviation ResizeArray<'T> to avoid conflicts with the F# List module.    
    // Note: In F# code, F# linked lists are usually preferred over
    // ResizeArray<'T> when an extendable collection is required.
    let parts = ResizeArray<_>()
    parts.Add({PartName = "crank arm" ; PartId = 1234})
    parts.Add({PartName = "chain ring"; PartId = 1334 })
    parts.Add({PartName = "regular seat"; PartId = 1434 })
    parts.Add({PartName = "banana seat"; PartId = 1444 })
    parts.Add({PartName = "cassette"; PartId = 1534 })
    parts.Add({PartName = "shift lever"; PartId = 1634 })

    // Write out the parts in the ResizeArray.  This will call the overridden ToString method
    // in the Part type
    printfn ""
    parts |> Seq.iter (fun p -> printfn "%O" p)

    // Check the ResizeArray for part #1734. This calls the IEquatable.Equals method 
    // of the Part type, which checks the PartId for equality.    
    printfn "\nContains(\"1734\"): %b" (parts.Contains({PartId=1734; PartName=""}))
    
    // Insert a new item at position 2.
    printfn "\nInsert(2, \"1834\")"
    parts.Insert(2, { PartName = "brake lever"; PartId = 1834 })

    // Write out all parts
    parts |> Seq.iter (fun p -> printfn "%O" p)

    printfn "\nParts[3]: %O" parts.[3]

    printfn "\nRemove(\"1534\")"
    // This will remove part 1534 even though the PartName is different, 
    // because the Equals method only checks PartId for equality.
    // Since Remove returns true or false, we need to ignore the result
    parts.Remove({PartId=1534; PartName="cogs"}) |> ignore

    // Write out all parts
    printfn ""
    parts |> Seq.iter (fun p -> printfn "%O" p)

    printfn "\nRemoveAt(3)"
    // This will remove the part at index 3.
    parts.RemoveAt(3)

    // Write out all parts
    printfn ""
    parts |> Seq.iter (fun p -> printfn "%O" p)

    0 // return an integer exit code

Nell'esempio seguente viene illustrato il Insert metodo , insieme a varie altre proprietà e metodi della List<T> classe generica. Dopo aver creato l'elenco, gli elementi vengono aggiunti. Il Insert metodo viene utilizzato per inserire un elemento al centro dell'elenco. L'elemento inserito è un duplicato, che verrà successivamente rimosso usando il Remove metodo .

using namespace System;
using namespace System::Collections::Generic;

void main()
{
    List<String^>^ dinosaurs = gcnew List<String^>();

    Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);

    dinosaurs->Add("Tyrannosaurus");
    dinosaurs->Add("Amargasaurus");
    dinosaurs->Add("Mamenchisaurus");
    dinosaurs->Add("Deinonychus");
    dinosaurs->Add("Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\nCapacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);

    Console::WriteLine("\nContains(\"Deinonychus\"): {0}",
        dinosaurs->Contains("Deinonychus"));

    Console::WriteLine("\nInsert(2, \"Compsognathus\")");
    dinosaurs->Insert(2, "Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    Console::WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);

    Console::WriteLine("\nRemove(\"Compsognathus\")");
    dinosaurs->Remove("Compsognathus");

    Console::WriteLine();
    for each(String^ dinosaur in dinosaurs )
    {
        Console::WriteLine(dinosaur);
    }

    dinosaurs->TrimExcess();
    Console::WriteLine("\nTrimExcess()");
    Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);

    dinosaurs->Clear();
    Console::WriteLine("\nClear()");
    Console::WriteLine("Capacity: {0}", dinosaurs->Capacity);
    Console::WriteLine("Count: {0}", dinosaurs->Count);
}

/* This code example produces the following output:

Capacity: 0

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

Capacity: 8
Count: 5

Contains("Deinonychus"): True

Insert(2, "Compsognathus")

Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus

dinosaurs[3]: Mamenchisaurus

Remove("Compsognathus")

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

TrimExcess()
Capacity: 5
Count: 5

Clear()
Capacity: 5
Count: 0
 */

List<string> dinosaurs = new List<string>();

Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);

dinosaurs.Add("Tyrannosaurus");
dinosaurs.Add("Amargasaurus");
dinosaurs.Add("Mamenchisaurus");
dinosaurs.Add("Deinonychus");
dinosaurs.Add("Compsognathus");
Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

Console.WriteLine("\nCapacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

Console.WriteLine("\nContains(\"Deinonychus\"): {0}",
    dinosaurs.Contains("Deinonychus"));

Console.WriteLine("\nInsert(2, \"Compsognathus\")");
dinosaurs.Insert(2, "Compsognathus");

Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

// Shows accessing the list using the Item property.
Console.WriteLine("\ndinosaurs[3]: {0}", dinosaurs[3]);

Console.WriteLine("\nRemove(\"Compsognathus\")");
dinosaurs.Remove("Compsognathus");

Console.WriteLine();
foreach(string dinosaur in dinosaurs)
{
    Console.WriteLine(dinosaur);
}

dinosaurs.TrimExcess();
Console.WriteLine("\nTrimExcess()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

dinosaurs.Clear();
Console.WriteLine("\nClear()");
Console.WriteLine("Capacity: {0}", dinosaurs.Capacity);
Console.WriteLine("Count: {0}", dinosaurs.Count);

/* This code example produces the following output:

Capacity: 0

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

Capacity: 8
Count: 5

Contains("Deinonychus"): True

Insert(2, "Compsognathus")

Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus

dinosaurs[3]: Mamenchisaurus

Remove("Compsognathus")

Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus

TrimExcess()
Capacity: 5
Count: 5

Clear()
Capacity: 5
Count: 0
 */

Imports System.Collections.Generic

Public Class Example

    Public Shared Sub Main()
        Dim dinosaurs As New List(Of String)

        Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)

        dinosaurs.Add("Tyrannosaurus")
        dinosaurs.Add("Amargasaurus")
        dinosaurs.Add("Mamenchisaurus")
        dinosaurs.Add("Deinonychus")
        dinosaurs.Add("Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        Console.WriteLine(vbLf & "Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)

        Console.WriteLine(vbLf & "Contains(""Deinonychus""): {0}", _
            dinosaurs.Contains("Deinonychus"))

        Console.WriteLine(vbLf & "Insert(2, ""Compsognathus"")")
        dinosaurs.Insert(2, "Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next
        ' Shows how to access the list using the Item property.
        Console.WriteLine(vbLf & "dinosaurs(3): {0}", dinosaurs(3))
        Console.WriteLine(vbLf & "Remove(""Compsognathus"")")
        dinosaurs.Remove("Compsognathus")

        Console.WriteLine()
        For Each dinosaur As String In dinosaurs
            Console.WriteLine(dinosaur)
        Next

        dinosaurs.TrimExcess()
        Console.WriteLine(vbLf & "TrimExcess()")
        Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)

        dinosaurs.Clear()
        Console.WriteLine(vbLf & "Clear()")
        Console.WriteLine("Capacity: {0}", dinosaurs.Capacity)
        Console.WriteLine("Count: {0}", dinosaurs.Count)
    End Sub
End Class

' This code example produces the following output:
'
'Capacity: 0
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'Capacity: 8
'Count: 5
'
'Contains("Deinonychus"): True
'
'Insert(2, "Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Compsognathus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'dinosaurs(3): Mamenchisaurus
'
'Remove("Compsognathus")
'
'Tyrannosaurus
'Amargasaurus
'Mamenchisaurus
'Deinonychus
'Compsognathus
'
'TrimExcess()
'Capacity: 5
'Count: 5
'
'Clear()
'Capacity: 5
'Count: 0


[<EntryPoint>]
let main argv = 
    // We refer to System.Collections.Generic.List<'T> by its type 
    // abbreviation ResizeArray<'T> to avoid conflict with the List module.    
    // Note: In F# code, F# linked lists are usually preferred over
    // ResizeArray<'T> when an extendable collection is required.
    let dinosaurs = ResizeArray<_>()
 
    // Write out the dinosaurs in the ResizeArray.
    let printDinosaurs() =
        printfn ""
        dinosaurs |> Seq.iter (fun p -> printfn "%O" p) 
 
    
    printfn "\nCapacity: %i" dinosaurs.Capacity
 
    dinosaurs.Add("Tyrannosaurus")
    dinosaurs.Add("Amargasaurus")
    dinosaurs.Add("Mamenchisaurus")
    dinosaurs.Add("Deinonychus")
    dinosaurs.Add("Compsognathus")
 
    printDinosaurs()
 
    printfn "\nCapacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    printfn "\nContains(\"Deinonychus\"): %b" (dinosaurs.Contains("Deinonychus"))
 
    printfn "\nInsert(2, \"Compsognathus\")"
    dinosaurs.Insert(2, "Compsognathus")
 
    printDinosaurs()
 
    // Shows accessing the list using the Item property.
    printfn "\ndinosaurs[3]: %s" dinosaurs.[3]
 
    printfn "\nRemove(\"Compsognathus\")"
    dinosaurs.Remove("Compsognathus") |> ignore
 
    printDinosaurs()
 
    dinosaurs.TrimExcess()
    printfn "\nTrimExcess()"
    printfn "Capacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    dinosaurs.Clear()
    printfn "\nClear()"
    printfn "Capacity: %i" dinosaurs.Capacity
    printfn "Count: %i" dinosaurs.Count
 
    0 // return an integer exit code
 
    (* This code example produces the following output:
 
Capacity: 0
 
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus
 
Capacity: 8
Count: 5
 
Contains("Deinonychus"): true
 
Insert(2, "Compsognathus")
 
Tyrannosaurus
Amargasaurus
Compsognathus
Mamenchisaurus
Deinonychus
Compsognathus
 
dinosaurs[3]: Mamenchisaurus
 
Remove("Compsognathus")
 
Tyrannosaurus
Amargasaurus
Mamenchisaurus
Deinonychus
Compsognathus
 
TrimExcess()
Capacity: 5
Count: 5
 
Clear()
Capacity: 5
Count: 0
    *)

Commenti

List<T> accetta null come valore valido per i tipi di riferimento e consente elementi duplicati.

Se Count è già uguale a Capacity, la capacità di viene aumentata riallocazione automatica della List<T> matrice interna e gli elementi esistenti vengono copiati nella nuova matrice prima dell'aggiunta del nuovo elemento.

Se index è uguale a Count, item viene aggiunto alla fine di List<T>.

Questo metodo è un'operazione O(n), dove n è Count.

Si applica a

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