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Silverlight DataBindings for 1.1 (Managed code)

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Silverlight DataBindings for 1.1 (Managed code)
 
 
文/黃忠成
 
   RC1方興未艾，RC2已在路上了，看來1.0 Release之日不遠了！前面一篇文章利用了PageMethods與JavaScript為Silverlight 1.0RC加上DataBindings的功能，此次舞台換到了Silverlight 1.1 Alpha Refresh及Visual Studio 2008 Beta 2上，與1.1時不同，這次已無法用單一的Web Site模式實作，基於ASP.NET Ajax與Silverlight所使用的CLR Runtime不同，我們必須將Silverlight與ASP.NET Ajax拆開，別誤會！這並非意味你無法將Silverlight與ASP.NET Ajax放在同一個虛擬目錄下，Silverlight 1.1使用的Binary目錄是ClientBin，ASP.NET是Bin，兩者並無衝突，限制只在於你必須將Silverlight與ASP.NET Ajax分成兩個Project來編譯，在Silverlight編譯完成後將.xaml、.js複製到ASP.NET Ajax的專案目錄下，再將.dll複製到ASP.NET Ajax的ClientBin目錄下即可。回到主題，在Silverlight 1.1中，實現Data Bindings除了可以用前一篇文章的JavaScript技巧外，還多了一個選擇，那就是使用C#等Managed的語言，SLDH.js的C#版本如下。
 
SLDH.cs
/////////////////////////////////////////////////////////////////////////
// Silverlight Data Binding Helper 0.1 for Silverlight 1.1 Alpha Refresh
/////////////////////////////////////////////////////////////////////////
using System;
using System.Text;
using System.IO;
using System.Net;
using System.Reflection;
using System.Linq;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using System.Windows.Browser.Net;
using System.Windows.Browser.Serialization;
 
namespace SilverlightDataHelper
{
    public class JSONDataRow
    {
        private List<object> _columns;
        private List<object> _values;
 
        public object this[int index]
        {
            get
            {
                return _values[index];
            }
        }
 
        public object this[string name]
        {
            get
            {
                for (int i = 0; i < _columns.Count; i++)
                {
                    if (((string)_columns[i]).Equals(name))
                        return _values[i];
                }
                return null;
            }
        }
 
        internal JSONDataRow(object[] columns, object[] values)
        {
            _columns = new List<object>(columns);
            _values = new List<object>(values);
        }
    }
 
    public class BindingData
    {
        private bool _bindingComplete = false;
        private string _bindingProperty = string.Empty;
        private string _bindingField = string.Empty;
        private FrameworkElement _control;
        private string _format = string.Empty;
        private PropertyInfo _cachedProp = null;
 
        public bool BindingComplete
        {
            get
            {
                return this._bindingComplete;
            }
        }
 
        public string BindingProperty
        {
            get
            {
                return _bindingProperty;
            }
        }
 
        public string BindingField
        {
            get
            {
                return _bindingField;
            }
        }
 
        public FrameworkElement Control
        {
            get
            {
                return _control;
            }
        }
 
        public string Format
        {
            get
            {
                return _format;
            }
            set
            {
                _format = value;
            }
        }
 
        public void UpdateValue(JSONDataRow dataItem)
        {
            if (_bindingComplete)
            {
                if (_cachedProp == null)
                {
                    _cachedProp = _control.GetType().GetProperty(_bindingProperty);
                    if (_cachedProp == null)
                        _bindingComplete = false;
                }
                if (_cachedProp != null && Format != string.Empty)
                {
                    if (_cachedProp.PropertyType == typeof(Uri))
                    {
                        Uri uri = new Uri(string.Format(Format,
                               dataItem[BindingField]), UriKind.Relative);
                        _cachedProp.SetValue(_control, uri, null);
                    }
                    else
                        _cachedProp.SetValue(_control, string.Format(Format,
dataItem[BindingField]), null);
                }
                else if (_cachedProp != null)
                    _cachedProp.SetValue(_control, dataItem[BindingField], null);
            }
        }
 
        public BindingData(FrameworkElement ctrl, string bindingExpression)
        {
            string[] bindings = bindingExpression.Split(';');
            _bindingComplete = false;
            _control = ctrl;
            for (int i = 0; i < bindings.Length; i++)
            {
                string[] temp = bindings[i].Split(':');
                if (temp.Length != 2)
                {
                    _bindingComplete = false;
                    return;
                }
                if (temp[0].ToLower() == "bindingfield")
                    _bindingField = temp[1];
                else if (temp[0].ToLower() == "bindingproperty")
                    _bindingProperty = temp[1];
                else if (temp[0].ToLower() == "format")
                    _format = temp[1];
            }
            if (_bindingField != string.Empty &&
               _bindingProperty != string.Empty)
                _bindingComplete = true;
        }
    }
 
    public class BindingContext
    {
        private Panel _container;
        private List<BindingData> _bindingControls = null;
        private bool _bindingComplete = false;
        private int _position = 0;
        private int _count = -1;
        private string _serviceUrl = string.Empty;
        private string _bindingMethod = string.Empty;
        private string _bindingCountMethod = string.Empty;
        private string _countMethod = string.Empty;
 
 
        public int Position
        {
            get
            {
                return _position;
            }
            set
            {
                if (_position != value && value < Count && value >= 0)
                {
                    _position = value;
                    UpdateBinding();
                }
            }
        }
 
        public int Count
        {
            get
            {
                return _count;
            }
        }
 
        public bool BindingComplete
        {
            get
            {
                return _bindingComplete;
            }
        }
 
        public List<BindingData> BindingControls
        {
            get
            {
                if (_bindingControls == null)
                    _bindingControls = new List<BindingData>();
                return _bindingControls;
            }
        }
 
        private void ChildWorker(FrameworkElement elem)
        {
            string exprsssion = elem.Tag == null ? string.Empty : elem.Tag;
            BindingData data = new BindingData(elem, exprsssion);
            if (data.BindingComplete)
                BindingControls.Add(data);
            if (elem is Panel)
            {
                Panel pnl = (Panel)elem;
                for (int i = 0; i < pnl.Children.Count; i++)
                {
                    if (pnl.Children[i] is FrameworkElement)
                        ChildWorker((FrameworkElement)pnl.Children[i]);
                }
            }
        }
 
        private void FetchCount()
        {
            BrowserHttpWebRequest request =
                    new BrowserHttpWebRequest(new Uri(_serviceUrl + "/" +
                                              _bindingCountMethod, UriKind.Relative));
            request.ContentType = "application/json; charset=utf-8";
            request.Method = "POST";
            request.ContentLength = 0;
            request.Referer = System.Windows.Browser.HtmlPage.DocumentUri.AbsolutePath;
            request.Accept = "/*/";
            HttpWebResponse response = request.GetResponse();
            StreamReader sr = new StreamReader(response.GetResponseStream());
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            string data = sr.ReadToEnd();
            _count = serializer.Deserialize<int>(data);
            sr.Close();
            response.Close();
            request.Close();
        }
 
        private JSONDataRow FetchData(int index)
        {
            BrowserHttpWebRequest request =
                new BrowserHttpWebRequest(new Uri(_serviceUrl + "/" +
                                          _bindingMethod, UriKind.Relative));
            JavaScriptSerializer serializer = new JavaScriptSerializer();
            request.ContentType = "application/json; charset=utf-8";
            request.Method = "POST";
            request.Referer = System.Windows.Browser.HtmlPage.DocumentUri.AbsolutePath;
            request.Accept = "/*/";
            Stream reqStream = request.GetRequestStream();
            byte[] buff = Encoding.UTF8.GetBytes("{index:" + index.ToString() + "}");
            reqStream.Write(buff, 0, buff.Length);
            request.ContentLength = buff.Length;
            HttpWebResponse response = request.GetResponse();
            StreamReader sr = new StreamReader(response.GetResponseStream());
            string data = sr.ReadToEnd();
            sr.Close();
            response.Close();
            request.Close();
            object[] parsedData = serializer.Deserialize<object[]>(data);
            return new JSONDataRow((object[])parsedData[0], (object[])parsedData[1]);
 
        }
 
        private void UpdateBinding()
        {
            JSONDataRow row = FetchData(Position);
            foreach (BindingData item in BindingControls)
                item.UpdateValue(row);
        }
 
        public void Initialize()
        {
            ChildWorker(_container);
            FetchCount();
            UpdateBinding();
        }
 
        public BindingContext(Panel container)
        {
            _container = container;
            if (_container.Tag == null)
            {
                _bindingComplete = false;
                return;
            }
            string[] parseBinding = container.Tag.Split(':');
            _bindingComplete = false;
            if (parseBinding.Length == 2 && parseBinding[0].ToLower() == "bindingcontext")
            {
                string[] bindingMethods = parseBinding[1].Split(',');
                if (bindingMethods.Length == 3)
                {
                    _serviceUrl = bindingMethods[0];
                    _bindingMethod = bindingMethods[1];
                    _bindingCountMethod = bindingMethods[2];
                    _bindingComplete = true;
                }
            }
            if (_bindingComplete)
                ChildWorker(container);
        }
    }
}
ㄟ...程式碼變長了哦~~~ >"<，在某些情況下，Managed Code不見得比JavaScript簡單吧！只是別忘了，這些程式碼是預先編譯後再下載到客戶端，由Silverlight CLR執行的，就理論上來說，執行效率應該比JavaScript好才對。由於Managed SLDH使用了另一種JSON格式來交換資料，所以.aspx.cs也要做一些調整。
Default.aspx.cs
using System;
using System.IO;
using System.Data;
using System.Collections.Generic;
using System.Data.SqlClient;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Xml.Linq;
using System.Web.Services;
 
public partial class _Default : System.Web.UI.Page
{
    private static DataTable BuildDataCache()
    {
        if (HttpRuntime.Cache["DataCache_Employees"] != null)
            return HttpRuntime.Cache["DataCache_Employees"] as DataTable;
        else
        {
            using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings["
ConnectionString"].ConnectionString))
            {
                SqlDataAdapter adapter = new SqlDataAdapter(
"SELECT * FROM Employees ORDER BY EmployeeID", conn);
                DataTable table = new DataTable("Employees");
                adapter.Fill(table);
                HttpRuntime.Cache["DataCache_Employees"] = table;
                return table;
            }
        }
    }
 
    private static List<object> BuildJSONRow(DataRow row)
    {
        List<object> result = new List<object>();
        List<string> columns = new List<string>();
        List<object> values = new List<object>();
        foreach (DataColumn col in row.Table.Columns)
        {
            columns.Add(col.ColumnName);
            values.Add(row.IsNull(col) ? string.Empty : row[col].ToString());
        }
        result.Add(columns);
        result.Add(values);
        return result;
    }
 
    [WebMethod]
    public static List<object> GetData(int index)
    {
        DataTable table = BuildDataCache();
        return BuildJSONRow(table.DefaultView[index].Row);
    }
 
    [WebMethod]
    public static int GetCount()
    {
        DataTable table = BuildDataCache();
        return table.DefaultView.Count;
    }
 
    protected void Page_Load(object sender, EventArgs e)
    {
        if (Request.QueryString["ID"] != null &&
           Request.QueryString["ID"].Length > 0)
        {
            using (SqlConnection conn = new SqlConnection(ConfigurationManager.ConnectionStrings[
"ConnectionString"].ConnectionString))
            {
                conn.Open();
                SqlCommand cmd = new SqlCommand(
"SELECT Photo FROM Employees WHERE EmployeeID = @ID", conn);
                cmd.Parameters.AddWithValue("@ID", Request.QueryString["ID"]);
                object data = cmd.ExecuteScalar();
                if (data != null && ((byte[])data).Length > 0)
                {
                    Response.Clear();
                    Response.BufferOutput = true;
                    Response.ContentType = "image/jpeg";
                    MemoryStream ms = new MemoryStream();
                    ms.Write(((byte[])data), 78, ((byte[])data).Length - 78);
                    MemoryStream jpegms = new MemoryStream();
                    System.Drawing.Image.FromStream(ms).Save(jpegms,
System.Drawing.Imaging.ImageFormat.Jpeg);
                    jpegms.Position = 0;
                    Response.OutputStream.Write(jpegms.GetBuffer(), 0, (int)jpegms.Length);
                    ms.Dispose();
                    jpegms.Dispose();
                    Response.Flush();
                    Response.End();
                }
            }
        }
    }
}
當需要做DataBindings時，只需要在.xaml.cs的Page_Loaded事件處理函式中建立此物件即可，見下面程式碼。
 
Page.xaml
<Canvasx:Name="parentCanvas"
        xmlns="http://schemas.microsoft.com/client/2007"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Loaded="Page_Loaded"
        x:Class="SilverlightProject1.Page;assembly=ClientBin/SilverlightProject1.dll"
        Width="640"
        Height="480"
        Background="White"
        >
           <CanvasName="DataDemo"Height="600"Width="800"
 Tag="BindingContext:Default.aspx,GetData,GetCount">
                     <Canvas.Background>
                                <LinearGradientBrush>
                                           <GradientStopColor="Yellow"Offset="0.0" />
                                           <GradientStopColor="Orange"Offset="0.5" />
                                           <GradientStopColor="Red"Offset="1.0" />
                                LinearGradientBrush>
                     Canvas.Background>
           <TextBlockTag="BindingField:EmployeeID;BindingProperty:Text"
          Name="txtEmployeeID"Width="144"Height="24"Canvas.Left="166"
        Canvas.Top="23"Text="A00001"TextWrapping="Wrap"/>
                     <TextBlockTag="BindingField:LastName;BindingProperty:Text"
           Name="txtLastName"Width="320"Height="24"Canvas.Left="500"
         Canvas.Top="23"Text="Alean Company"TextWrapping="Wrap"/>
                     <TextBlockTag="BindingField:FirstName;BindingProperty:Text"Name="txtFirstName"
                      Width="320"Height="24"Canvas.Left="166"Canvas.Top="72"
                      Text="Jeffray"TextWrapping="Wrap"/>
                     <TextBlockTag="BindingField:Title;BindingProperty:Text"
                      Name="txtTitle"Width="576"Height="24"Canvas.Left="166"
                      Canvas.Top="122"Text="Taipen 101"TextWrapping="Wrap"/>
                     <TextBlockTag="BindingField:HireDate;BindingProperty:Text"Name="txtHireDate"
                      Width="576"Height="24"Canvas.Left="166"Canvas.Top="171"
                      Text="2005/3/4"TextWrapping="Wrap"/>
                     <ImageName="imgPhoto" 
Tag="BindingField:EmployeeID;BindingProperty:Source;Format:Default.aspx?ID={0}"
      Width="357"Height="206"Canvas.Left="400"Canvas.Top="301">
                                <Image.Triggers>
                                           <EventTriggerRoutedEvent="Image.Loaded">
                                                     <BeginStoryboard>
                                                                <StoryboardName="imgAnimation">
                                                                           <DoubleAnimation
                                                                           Storyboard.TargetName="imgPhoto"
                                                                           Storyboard.TargetProperty="Opacity"
                                                                           From="0.0"To="1.0"Duration="0:0:6"/>
                                                                Storyboard>
                                                     BeginStoryboard>
                                           EventTrigger>
                                Image.Triggers>
                     Image>
                     <TextBlockName="txtLabel1"Width="114"Height="24"Canvas.Left="18"
           Canvas.Top="23"Text="Employee ID:"TextWrapping="Wrap"/>
                     <TextBlockName="txtLabel1_Copy"Width="120"Height="24"Canvas.Left="349"
            Canvas.Top="23"Text="Last Name:"TextWrapping="Wrap"/>
                     <TextBlockName="txtLabel1_Copy1"Width="130"Height="24"Canvas.Left="18"
            Canvas.Top="72"Text="First Name:"TextWrapping="Wrap"/>
                     <TextBlockName="txtLabel1_Copy2"Width="104"Height="24"Canvas.Left="18"
           Canvas.Top="122"Text="Title :"TextWrapping="Wrap"/>
                     <TextBlockName="txtLabel1_Copy3"Width="93"Height="24"Canvas.Left="18"
            Canvas.Top="171"Text="Hire Date:"TextWrapping="Wrap"/>
           Canvas>
           <TextBlockCanvas.Left="100"Canvas.Top="200"
Text="Prev"MouseLeftButtonDown="OnPrevClick"/>
           <TextBlockCanvas.Left="150"Canvas.Top="200"
Text="Next"MouseLeftButtonDown="OnNextClick"/>
Canvas>
 
Page.xaml.cs
using System;
using System.Linq;
using System.Collections.Generic;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
 
namespace SilverlightProject1
{
    public partial class Page : Canvas
    {
        private SilverlightDataHelper.BindingContext _context = null;
        public void Page_Loaded(object o, EventArgs e)
        {
            // Required to initialize variables
            InitializeComponent();
            _context = new SilverlightDataHelper.BindingContext(FindName("DataDemo") as Panel);
            _context.Initialize();
        }
 
        void OnPrevClick(object sender, EventArgs args)
        {
            if (_context.Position > 0)
            {
                _context.Position--;
                ((Storyboard)FindName("imgAnimation")).Begin();
            }
        }
 
        void OnNextClick(object sender, EventArgs args)
        {
            if (_context.Position < _context.Count)
            {
                _context.Position++;
                ((Storyboard)FindName("imgAnimation")).Begin();
            }
        }
    }
}
下圖是執行畫面。
 
http://www.dreams.idv.tw/~code6421/files/SLDataDemo_11.zip
(你需要將Northwind.mdf、Northwind_log.ldf複製到App_Data目錄下，或是修改web.config中的ConnectionString來連結到北風資料庫)
 

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