VS 2008 SP1 + .NET 3.5 SP1 (7) - ADO.NET Data Services 資料服務

簡介

ADO.NET Data Services (後稱 WCF Data Services) 讓資料以 REST 風格的 URI 公開，支援 LINQ 查詢、JSON/AtomPub 格式。本文以 Northwind 為例，示範服務端與用戶端實作。

服務端實作 - Service.cs

public class Service : DataService<VS2008SP1.Business.NorthwindEntities> {
    public static void InitializeService(IDataServiceConfiguration config) {
        // 開放所有實體集的完整存取權限
        config.SetEntitySetAccessRule("*", EntitySetRights.All);
    }

    // 查詢攔截器：限制 Orders 僅回傳 ContactName 為 Paul Henriot 的資料
    [QueryInterceptor("Orders")]
    public Expression<Func<Orders, bool>> FilterOrders() {
        return o => o.Customers.ContactName == "Paul Henriot";
    }
}

用戶端 CRUD 示範 - Demo.aspx.cs

public partial class DataServices_Demo : System.Web.UI.Page {
    Uri _uri = new Uri("https://localhost:7002/DataServices/Service.svc/", UriKind.Absolute);

    void BindData() {
        NorthwindEntities ctx = new NorthwindEntities(_uri);
        GridView1.DataSource = ctx.Categories;
        GridView1.DataBind();
    }

    protected void btnAddCategory_Click(object sender, EventArgs e) {
        NorthwindEntities ctx = new NorthwindEntities(_uri);
        Categories category = new Categories { CategoryName = txtCategoryName.Text, Description = txtDescription.Text };
        ctx.MergeOption = MergeOption.AppendOnly;
        ctx.AddToCategories(category);

        // 批次新增 10 筆產品並建立關聯
        for (int i = 0; i < 10; i++) {
            var product = new Products { ProductName = "測試用" + i };
            product.Categories = category;
            ctx.AddToProducts(product);
            ctx.SetLink(product, "Categories", category); // 多對一
        }
        ctx.SaveChanges(SaveChangesOptions.Batch);
        BindData();
    }

    protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e) {
        NorthwindEntities ctx = new NorthwindEntities(_uri);
        var categoryId = (int)GridView1.DataKeys[e.RowIndex].Value;
        var category = ctx.Categories.Where(p => p.CategoryID == categoryId).First();
        ctx.LoadProperty(category, "Products"); // 載入導航屬性以便級聯刪除
        foreach (var product in category.Products) ctx.DeleteObject(product);
        ctx.DeleteObject(category);
        ctx.SaveChanges();
        BindData();
    }
    // ... 更新、查詢明細等事件處理
}

進階查詢技巧 - Demo2.aspx.cs

void Demo() {
    // URI 語法查詢
    DataServiceContext ctx = new DataServiceContext(_uri);
    DataServiceQuery<Categories> categories = ctx.CreateQuery<Categories>("/Categories");
    foreach (var c in categories) result.InnerHtml += c.CategoryID + ",";
}

void Demo2() {
    // 非同步查詢
    DataServiceQuery<Categories> query = ctx.CreateQuery<Categories>("/Categories");
    query.BeginExecute(ar => {
        foreach (var c in query.EndExecute(ar)) result.InnerHtml += c.CategoryID + ",";
    }, null);
}

void Demo3() {
    // 查詢攔截器效果驗證
    NorthwindEntities ctx = new NorthwindEntities(_uri);
    foreach (var o in ctx.Orders) result.InnerHtml += o.OrderID + ","; // 只會得到 Paul Henriot 的訂單
}

void Demo4() {
    // 要求 JSON 格式回應
    WebClient client = new WebClient();
    client.Headers.Add("accept", "application/json");
    result.InnerHtml += HttpUtility.HtmlEncode(client.DownloadString(_uri));
}

重點摘要

• DataService<T> 為服務進入點，IDataServiceConfiguration.SetEntitySetAccessRule 控制權限。
• QueryInterceptorAttribute 實作資料列層級安全性過濾。
• 用戶端使用 DataServiceContext 與 DataServiceQuery，支援 LINQ、URI 語法、非同步、批次更新。
• 可透過 HTTP Accept 標頭切換回應格式 (JSON/Atom)。

完整原始碼：https://www.bianceng.net/dotnet/201212/806.htm