HOW TO：使用 EntityCommand 執行參數型 Entity SQL 查詢 (EntityClient)

本主題提供的範例將示範如何使用 EntityCommand 以參數執行 實體 SQL 查詢。

若要執行這個範例中的程式碼

1. 將 AdventureWorks Sales Model 加入至專案中，並將專案設定成使用 Entity Framework。若要這麼做，必須執行下列其中一項：

   • 如果已經安裝 Entity Dada Model 工具，請完成 HOW TO：使用 Entity Data Model 精靈 (Entity Framework) 中的程序。

   • 不然的話，請完成 HOW TO：手動設定 Entity Framework 專案和 HOW TO：以手動方式定義 Entity Data Model (Entity Framework) 中的程序。

2. 在應用程式的字碼頁中加入下列 using 陳述式 (在 Visual Basic 中為 Imports)：

   Imports System
   Imports System.Collections.Generic
   Imports System.Collections
   Imports System.Data.Common
   Imports System.Data
   Imports System.Data.SqlClient
   Imports System.Data.EntityClient
   Imports System.Data.Metadata.Edm
   Imports System.IO
   ' Add AdventureWorksModel prepended with the root namespace for the project.
   'Imports ProjectName.AdventureWorksModel
   

   using System;
   using System.Collections.Generic;
   using System.Collections;
   using System.Data.Common;
   using System.Data;
   using System.IO;
   using System.Data.SqlClient;
   using System.Data.EntityClient;
   using AdventureWorksModel;
   using System.Data.Metadata.Edm;
   

範例

下列範例示範如何建構具有兩個參數的查詢字串。然後它會建立 EntityCommand、將兩個參數加入到該 EntityCommand 的 EntityParameter 集合，並逐一查看 Contact 項目的集合。

Using conn As EntityConnection = New EntityConnection("name=AdventureWorksEntities")
    conn.Open()

    ' Create a query that takes two parameters.
    Dim esqlQuery As String = "SELECT VALUE Contact FROM AdventureWorksEntities.Contact " & _
        "AS Contact WHERE Contact.LastName = @ln AND " & _
        "Contact.FirstName = @fn"

    Try
        Using cmd As EntityCommand = New EntityCommand(esqlQuery, conn)
            ' Create two parameters and add them to 
            ' the EntityCommand's Parameters collection 
            Dim param1 As New EntityParameter
            param1.ParameterName = "ln"
            param1.Value = "Adams"
            Dim param2 As New EntityParameter
            param2.ParameterName = "fn"
            param2.Value = "Frances"
            cmd.Parameters.Add(param1)
            cmd.Parameters.Add(param2)

            Using rdr As DbDataReader = cmd.ExecuteReader(CommandBehavior.SequentialAccess)
                ' Iterate through the collection of Contact items.
                Do While rdr.Read
                    Console.WriteLine(rdr.Item("FirstName"))
                    Console.WriteLine(rdr.Item("LastName"))
                Loop
            End Using
        End Using
    Catch ex As EntityException
        Console.WriteLine(ex.ToString())
    End Try
    conn.Close()
End Using

using (EntityConnection conn =
    new EntityConnection("name=AdventureWorksEntities"))
{
    conn.Open();
    // Create a query that takes two parameters.
    string esqlQuery =
        @"SELECT VALUE Contact FROM AdventureWorksEntities.Contact 
                    AS Contact WHERE Contact.LastName = @ln AND
                    Contact.FirstName = @fn";

    try
    {
        using (EntityCommand cmd = new EntityCommand(esqlQuery, conn))
        {
            // Create two parameters and add them to 
            // the EntityCommand's Parameters collection 
            EntityParameter param1 = new EntityParameter();
            param1.ParameterName = "ln";
            param1.Value = "Adams";
            EntityParameter param2 = new EntityParameter();
            param2.ParameterName = "fn";
            param2.Value = "Frances";

            cmd.Parameters.Add(param1);
            cmd.Parameters.Add(param2);

            using (DbDataReader rdr = cmd.ExecuteReader(CommandBehavior.SequentialAccess))
            {
                // Iterate through the collection of Contact items.
                while (rdr.Read())
                {
                    Console.WriteLine(rdr["FirstName"]);
                    Console.WriteLine(rdr["LastName"]);
                }
            }
        }
    }
    catch (EntityException ex)
    {
        Console.WriteLine(ex.ToString());
    }
    conn.Close();
}

另請參閱

工作

HOW TO：執行參數化查詢 (Entity Framework)

概念

Entity SQL 語言

其他資源

使用 EntityClient (Entity Framework 工作)