DataSet DataRelation

DataTable.ChildRelations

Gets the collection of child relations for this DataTable.

A DataRelation defines the relationship between two tables. Typically, two tables are linked through a single field that contains the same data. For example, a table which contains address data may have a single field containing codes that represent countries/regions. A second table that contains country/region data will have a single field that contains the code that identifies the country/region, and it is this code which is inserted into the corresponding field in the first table. A DataRelation, then, contains at least four pieces of information: (1) the name of the first table, (2) the column name in the first table, (3) the name of the second table, and (4) the column name in the second table.

   private static void GetChildRowsFromDataRelation()
    {
        /* For each row in the table, get the child rows using the
        ChildRelations. For each item in the array, print the value
        of each column. */
        DataTable table = CreateDataSet().Tables["Customers"];
        DataRow[] childRows;
        foreach(DataRelation relation in table.ChildRelations)
        {
            foreach(DataRow row in table.Rows)
            {
                PrintRowValues(new DataRow[] {row}, "Parent Row");
                childRows = row.GetChildRows(relation);
                // Print values of rows.
                PrintRowValues(childRows, "child rows");
            }
        }
    }

    public static DataSet CreateDataSet()
    {
        // create a DataSet with one table, two columns
        DataSet dataSet = new DataSet();

        // create Customer table
        DataTable table = new DataTable("Customers");
        dataSet.Tables.Add(table);
        table.Columns.Add("customerId", typeof(int)).AutoIncrement = true;
        table.Columns.Add("name", typeof(string));
        table.PrimaryKey = new DataColumn[] { table.Columns["customerId"] };

        // create Orders table
        table = new DataTable("Orders");
        dataSet.Tables.Add(table);
        table.Columns.Add("orderId", typeof(int)).AutoIncrement = true;
        table.Columns.Add("customerId", typeof(int));
        table.Columns.Add("amount", typeof(double));
        table.PrimaryKey = new DataColumn[] { table.Columns["orderId"] };

        // create relation
        dataSet.Relations.Add(dataSet.Tables["Customers"].Columns["customerId"],
            dataSet.Tables["Orders"].Columns["customerId"]);

        // populate the tables
        int orderId = 1;
        for(int customerId=1; customerId<=10; customerId++)
        {
            // add customer record
            dataSet.Tables["Customers"].Rows.Add(
                new object[] { customerId,
                string.Format("customer{0}", customerId) });

            // add 5 order records for each customer
            for(int i=1; i<=5; i++)
            {
                dataSet.Tables["Orders"].Rows.Add(
                    new object[] { orderId++, customerId, orderId * 10 });
            }
        }

        return dataSet;
    }

    private static void PrintRowValues(DataRow[] rows, string label)
    {
        Console.WriteLine("\n{0}", label);
        if(rows.Length <= 0)
        {
            Console.WriteLine("no rows found");
            return;
        }
        foreach(DataRow row in rows)
        {
            foreach(DataColumn column in row.Table.Columns)
            {
                Console.Write("\table {0}", row[column]);
            }
            Console.WriteLine();
        }
    }

DataRow.GetParentRows Method

DataRow.GetChildRows Method

DataTable.Constraints Property

private void CreateConstraint(DataSet dataSet,
    string table1, string table2, string column1, string column2)
{
    ForeignKeyConstraint idKeyRestraint = new
        ForeignKeyConstraint(dataSet.Tables[table1].Columns[column1],
        dataSet.Tables[table2].Columns[column2]);

    // Set null values when a value is deleted.
    idKeyRestraint.DeleteRule = Rule.SetNull;
    idKeyRestraint.UpdateRule = Rule.Cascade;

    // Set AcceptRejectRule to cascade changes.
    idKeyRestraint.AcceptRejectRule = AcceptRejectRule.Cascade;

    dataSet.Tables[table1].Constraints.Add(idKeyRestraint);
    dataSet.EnforceConstraints = true;
}

DataTable Constraints

http://msdn.microsoft.com/en-us/library/st1t2c35(v=vs.110).aspx

ForeignKeyConstraint

UniqueConstraint

DataSet DataRelation,布布扣,bubuko.com