DataTable.PrimaryKey 屬性

定義

命名空間:

System.Data

組件:

System.Data.Common.dll

來源:

DataTable.cs

取得或設定資料行的陣列，這些資料行是做為資料表 (Data Table) 之主索引鍵。

public:
 property cli::array <System::Data::DataColumn ^> ^ PrimaryKey { cli::array <System::Data::DataColumn ^> ^ get(); void set(cli::array <System::Data::DataColumn ^> ^ value); };

[System.ComponentModel.TypeConverter(typeof(System.Data.PrimaryKeyTypeConverter))]
public System.Data.DataColumn[] PrimaryKey { get; set; }

[<System.ComponentModel.TypeConverter(typeof(System.Data.PrimaryKeyTypeConverter))>]
member this.PrimaryKey : System.Data.DataColumn[] with get, set

Public Property PrimaryKey As DataColumn()

屬性值

DataColumn[]

DataColumn 物件的陣列。

屬性

TypeConverterAttribute

例外狀況

DataException

索引鍵為外部索引鍵。

範例

第一個範例示範如何傳 DataTable 回 中所 DataGrid顯示 的主鍵數據行。 第二個 DataTable範例示範如何設定的主鍵數據行。

private void GetPrimaryKeys(DataTable table)
{
    // Create the array for the columns.
    DataColumn[] columns;
    columns = table.PrimaryKey;

    // Get the number of elements in the array.
    Console.WriteLine($"Column Count: {columns.Length}");
    for (int i = 0; i < columns.Length; i++)
    {
        Console.WriteLine($"{columns[i].ColumnName} {columns[i].DataType}");
    }
}

private void SetPrimaryKeys()
{
    // Create a new DataTable and set two DataColumn objects as primary keys.
    var table = new DataTable();
    var keys = new DataColumn[2];
    DataColumn column;

    // Create column 1.
    column = new DataColumn();
    column.DataType = Type.GetType("System.String");
    column.ColumnName= "FirstName";

    // Add the column to the DataTable.Columns collection.
    table.Columns.Add(column);

    // Add the column to the array.
    keys[0] = column;

    // Create column 2 and add it to the array.
    column = new DataColumn();
    column.DataType = Type.GetType("System.String");
    column.ColumnName = "LastName";
    table.Columns.Add(column);

    // Add the column to the array.
    keys[1] = column;

    // Set the PrimaryKeys property to the array.
    table.PrimaryKey = keys;
}

Private Sub GetPrimaryKeys(table As DataTable)
    ' Create the array for the columns.
    Dim columns As DataColumn()
    columns = table.PrimaryKey

    ' Get the number of elements in the array.
    Console.WriteLine($"Column Count: {columns.Length}")
    For i = 0 To columns.GetUpperBound(0)
        Console.WriteLine($"{columns(i).ColumnName} {columns(i).DataType}")
    Next
End Sub

Private Sub SetPrimaryKeys()
    ' Create a new DataTable and set two DataColumn objects as primary keys.
    Dim table As New DataTable()
    Dim keys(1) As DataColumn
    Dim column  As DataColumn

    ' Create column 1.
    column = New DataColumn()
    column.DataType = Type.GetType("System.String")
    column.ColumnName= "FirstName"

    ' Add the column to the DataTable.Columns collection.
    table.Columns.Add(column)
    ' Add the column to the array.
    keys(0) = column

    ' Create column 2 and add it to the array.
    column = New DataColumn()
    column.DataType = Type.GetType("System.String")
    column.ColumnName = "LastName"
    table.Columns.Add(column)

    ' Add the column to the array.
    keys(1) = column

    ' Set the PrimaryKeys property to the array.
    table.PrimaryKey = keys
End Sub

備註

數據表的主鍵必須是唯一的，才能識別數據表中的記錄。 也可以讓包含由兩個或多個數據行組成的主鍵的數據表。 當單一數據行不能包含足夠的唯一值時，就會發生這種情況。 例如，兩個數據行主鍵可能包含 「OrderNumber」 和 「ProductID」 資料行。 因為主鍵可以由多個數據行組成，所以 PrimaryKey 屬性是由 對象的陣列 DataColumn 所組成。

另請參閱

• DataColumn
• PrimaryKey
• DataColumnCollection
• DataTables