Web/EntityFramework/ObjectQuery.aspx.cs

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

using System.Data.Objects;
using System.Data.Objects.DataClasses;
using System.Data.EntityClient;
using System.Data;
using System.Data.Common;

using VS2008SP1.Business;

public partial class EntityFramework_ObjectQuery : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!Page.IsPostBack)
        {
            Demo();

            result.InnerHtml += "<br />";

            Demo2();

            result.InnerHtml += "<br />";

            Demo3();

            result.InnerHtml += "<br />";

            Demo4();
        }
    }

    private void Demo()
    {
        using (var ctx = new NorthwindEntities())
        {
            string esql = "select value c from NorthwindEntities.Categories as c";

            // ObjectQuery<T> - 通过 Entity SQL 或 查询语法 或 Linq 方法对概念模型做查询
            // ObjectContext.CreateQuery<T>(Entity SQL) - 根据 esql 创建一个 ObjectQuery<T> 。（延迟）
            ObjectQuery<Categories> query = ctx.CreateQuery<Categories>(esql);

            foreach (var c in query)
            {
                result.InnerHtml += c.CategoryName + "<br />";
            }
        }

        /*
        SELECT 
        [Extent1].[CategoryID] AS [CategoryID], 
        [Extent1].[CategoryName] AS [CategoryName], 
        [Extent1].[Description] AS [Description], 
        [Extent1].[Picture] AS [Picture]
        FROM [dbo].[Categories] AS [Extent1]