結果多映射

描述

可以使用擴展方法執(zhí)行查詢并將結果映射到具有關系的強類型列表。

關系可以是：

• 一對一
• 一對多

這些擴展方法可以從IDbConnection類型的任意對象中調用。

案例 - 查詢多映射（一對一）

Query方法可以執(zhí)行查詢并將結果映射到具有一對一關系的強類型列表。

string sql = "SELECT * FROM Invoice AS A INNER JOIN InvoiceDetail AS B ON A.InvoiceID = B.InvoiceID;";

using (var connection = My.ConnectionFactory())
{
    connection.Open();

    var invoices = connection.Query<Invoice, InvoiceDetail, Invoice>(
            sql,
            (invoice, invoiceDetail) =>
            {
                invoice.InvoiceDetail = invoiceDetail;
                return invoice;
            },
            splitOn: "InvoiceID")
        .Distinct()
        .ToList();
}

案例 - 查詢多映射（一對多）

Query方法可以執(zhí)行查詢并將結果映射到具有一對多關系的強類型列表。

string sql = "SELECT * FROM Invoice AS A INNER JOIN InvoiceItem AS B ON A.InvoiceID = B.InvoiceID;";

using (var connection = My.ConnectionFactory())
{
    connection.Open();

    var invoiceDictionary = new Dictionary<int, Invoice>();

    var invoices = connection.Query<Invoice, InvoiceItem, Invoice>(
            sql,
            (invoice, invoiceItem) =>
            {
                Invoice invoiceEntry;

                if (!invoiceDictionary.TryGetValue(invoice.InvoiceID, out invoiceEntry))
                {
                    invoiceEntry = invoice;
                    invoiceEntry.Items = new List<InvoiceItem>();
                    invoiceDictionary.Add(invoiceEntry.InvoiceID, invoiceEntry);
                }

                invoiceEntry.Items.Add(invoiceItem);
                return invoiceEntry;
            },
            splitOn: "InvoiceID")
        .Distinct()
        .ToList();
}