DataTable.PrimaryKey 属性

第一个示例显示如何返回在 DataGrid 中显示的 DataTable 的主键列。第二个示例演示如何为 DataTable 设置主键列。

Visual Basic

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.ToString())
Dim i As Integer
For i = 0 To columns.GetUpperBound(0)
Console.WriteLine(columns(i).ColumnName & columns(i).DataType.ToString())
Next i
End Sub
Private Sub SetPrimaryKeys()
' Create a new DataTable and set two DataColumn objects as primary keys.
Dim table As DataTable = new DataTable()
Dim keys(2) As DataColumn
Dim column  As DataColumn
' Create column 1.
column = New DataColumn()
column.DataType = System.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 = System.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

C#

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.
DataTable table = new DataTable();
DataColumn[] keys = new DataColumn[2];
DataColumn column;
// Create column 1.
column = new DataColumn();
column.DataType = System.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 = System.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;
}