mojoportal学习笔记之How to Write a Provider Model

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mojoportal学习笔记之How to Write a Provider Model

    在学习 mojoportal时，看到mojoportal调用editor使用了provider，顺便温习一下provider模式。

    How to Write a Provider Model

    原文地址： http://dotnetslackers.com/articles/designpatterns/HowToWriteAProviderModel.aspx)

    这里只是简要的学习一下，做个笔记

   自定义建立provider ,分四步
Main data provider class.
Data provider collection class.
Data provider configuration class.
Data provider manager class.
第一步： Main Data Provider Class

Main Data Provider Class 也是一个抽象类，定义了所有相关的数据操作方法。

这个抽象的数据操作方法类必须继承自System.Configuration.Provider.ProviderBase 基类

举例：

1using System;
2using System.Collections.Generic;
3using System.Linq;
4using System.Text;
5using System.Configuration.Provider;
6
7namespace SampleProvider
8{
9    public abstract class DataProvider : ProviderBase
10    {
11        // Adds a text value for a specified ID to the storage
12        public abstract void AddText(int id, string text);
13
14        // Gets the text associated to a specified ID
15        public abstract string GetText(int id);
16    }
17}

正如你看到的，这个main provider class 继承自ProviderBase抽象类，定义了两个抽象方法，这两个方法需要被不同的provider 实现

你应该明白，这个main provider class 是你的provider 中抽象的方法定义的地方。

第二步：Data Provider Collection

provider 集合类，继承自System.Configuration.ProviderCollection基类

ProviderCollection 类暴露了几个方法处理配置文件中定义的provider类

关键的一点是，providerCollection类返回main provider class 一个实例

代码如下：

1Listing 2: Data provider collection class
2using System;
3using System.Collections.Generic;
4using System.Linq;
5using System.Text;
6using System.Configuration.Provider;
7
8namespace SampleProvider
9{
10    public class DataProviderCollection : ProviderCollection
11    {
12        // Return an instance of DataProvider
13        // for a specified provider name
14        new public DataProvider this[string name]
15        {
16            get { return (DataProvider)base[name]; }
17        }
18    }
19}

第三步：Data Provider Configuration

下一步工作是写一个 data provider configuration 类，用来读取配置文件

这个类需要引用System.Configuration.ConfigSection命名空间. 在你的配置类中，你需要定义一个类型为System.Configuraiton.ProviderSettingsCollection的属性。这个属性会从基类中返回一个实例。这个类中，所有属性必须装饰 ConfigurationProperty 标签 1using System;    2using System.Collections.Generic;    3using System.Linq;    4using System.Text;    5using System.Configuration;    6   7namespace SampleProvider    8{    9    public class DataProviderConfiguration : ConfigurationSection    10    {    11        [ConfigurationProperty("providers")]    12        public ProviderSettingsCollection Providers    13        {    14            get   15            {    16                return (ProviderSettingsCollection)base["providers"];    17            }    18        }    19   20        [ConfigurationProperty("default", DefaultValue = "SqlProvider")]    21        public string Default    22        {    23            get   24            {    25                return (string)base["default"];    26            }    27            set   28            {    29                base["default"] = value;    30            }    31        }    32    }    33}   上面的代码中，定义了2个属性，第一个属性类型是ProviderSettingsCollection，名称是Providers 它映射到配置文件的<providers /> 元素第二个方法设置了默认provider的名称，默认使用sqlProvider. 第四步：Data Provider Manager 这一步中你不需要继承接口或基类，只要根据你的需求来写。 data provider Manager的主要目的是初始化一个具体的 provider类，并在内存中加载配置信息。初始化时，你需要为你的data provider获取配置信息，并在内存中建立一个具体的实例。为了使代码工作，你的Data Provider Manager类中必须包含一个静态的public Initialize方法代码如下： 1using System;    2using System.Collections.Generic;    3using System.Linq;    4using System.Text;    5using System.Configuration;    6using System.Web.Configuration;    7   8namespace SampleProvider    9{    10    public class DataProviderManager    11    {    12        private static DataProvider defaultProvider;    13        private static DataProviderCollection providers;    14   15        static DataProviderManager()    16        {    17            Initialize();    18        }    19   20        private static void Initialize()    21        {    22            DataProviderConfiguration configuration =    23                (DataProviderConfiguration)    24                ConfigurationManager.GetSection("SampleProvider");    25   26            if (configuration == null)    27                throw new ConfigurationErrorsException    28                    ("SampleProvider configuration section is not set correctly.");    29   30            providers = new DataProviderCollection();    31   32            ProvidersHelper.InstantiateProviders(configuration.Providers    33                , providers, typeof(DataProvider));    34   35            providers.SetReadOnly();    36   37            defaultProvider = providers[configuration.Default];    38   39            if (defaultProvider == null)    40                throw new Exception("defaultProvider");    41        }    42   43        public static DataProvider Provider    44        {    45            get   46            {    47                return defaultProvider;    48            }    49        }    50   51        public static DataProviderCollection Providers    52        {    53            get   54            {    55                return providers;    56            }    57        }    58    }    59}

Default Sql Data Provider

using System;
2

using System.Collections.Generic;
3

using System.Linq;
4

using System.Text;
5

using System.Data.SqlClient;
6

using System.Configuration;
7

using System.Collections.Specialized;
8

namespace SampleProvider
10

{
11

public class SqlDataProvider : DataProvider
12

{
13

private string _connectionString = string.Empty;
14

public override void Initialize(string name, NameValueCollection config)
16

{
17

base.Initialize(name, config);
18

this._connectionString = config["connectionString"];
20

if (string.IsNullOrEmpty(this._connectionString))
22

throw new ConfigurationErrorsException
23

("connectionString must be set to the appropriate value");
24

}
25

public override void AddText(int id, string text)
27

{
28

using (SqlConnection connection = new SqlConnection(this._connectionString))
29

{
30

// For real world scnearios use parameterized SQL to avoid SQL injections!
31

string commandText = string.Format
32

("INSERT INTO SampleTable (Id, Value) VALUES ({0}, '{1}')", id, text);
33

SqlCommand command = new SqlCommand(commandText, connection);
34

command.CommandType = System.Data.CommandType.Text;
35

connection.Open();
37

command.ExecuteNonQuery();
38

connection.Close();
39

command.Dispose();
40

}
41

}
42

public override string GetText(int id)
44

{
45

string result = string.Empty;
46

using (SqlConnection connection = new SqlConnection(this._connectionString))
48

{
49

string commandText = string.Format("SELECT Value FROM SampleTable WHERE Id = {0}", id);
50

SqlCommand command = new SqlCommand(commandText, connection);
51

command.CommandType = System.Data.CommandType.Text;
52

connection.Open();
54

result = command.ExecuteScalar() as string;
56

connection.Close();
58

command.Dispose();
59

}
60

return result;
62

}
63

}
64

添加配置文件

1：在<configSections> </configSections>中添加代码如下

<configSections>
<section name="SampleProvider"
           type="SampleProvider.DataProviderConfiguration, SampleProvider" />
</configSections>

2<configuration > </configuration>中添加代码如下

<SampleProvider default="SqlProvider">
<providers>
    <add name="SqlProvider"
        type="SampleProvider.SqlDataProvider, SampleProvider"
        connectionString="Data Source=.\SQLEXPRESS;AttachDbFilename=|DataDirectory|\DB.mdf;Integrated
curity=True;User Instance=True" />
</providers>
</SampleProvider>

测试代码如下：

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="Default.aspx.cs" Inherits="SampleSite._Default" %>
2

<%@ Import Namespace="SampleProvider" %>
4

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
5

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
6

<html xmlns="http://www.w3.org/1999/xhtml">
7

protected void btnAdd_Click(object sender, EventArgs e)
10

{
11

try
12

{
13

DataProviderManager.Provider.AddText
14

(Convert.ToInt32(txtId.Text), txtValue.Text);
15

lblResult.Text = "Data added successfully!";
16

}
17

catch (Exception ex)
18

{
19

lblResult.Text = ex.Message + "<br /> " + ex.StackTrace;
20

}
21

}
22

protected void btnSelect_Click(object sender, EventArgs e)
24

{
25

try
26

{
27

lblData.Text = DataProviderManager.Provider.GetText
28

(Convert.ToInt32(txtIdToSelect.Text));
29

}
30

catch (Exception ex)
31

{
32

lblData.Text = ex.Message + "<br /> " + ex.StackTrace;
33

}
34

}
35

</script>
36

<head runat="server">
38

<title>Untitled Page</title>
39

</head>
40

<body>
41

<form id="form1" runat="server">
42

<div>
43

<h1>
44

Add Data</h1>
45

Enter ID: <asp:TextBox ID="txtId" runat="server"></asp:TextBox><br />
46

Enter Value: <asp:TextBox ID="txtValue" runat="server"></asp:TextBox><br />
47

<asp:Button ID="btnAdd" runat="server" Text="Add" OnClick="btnAdd_Click" /><br />
48

<asp:Label ID="lblResult" runat="server" Text=""></asp:Label>
49

</div>
50

<div>
51

<h1>
52

Select Data</h1>
53

Enter ID: <asp:TextBox ID="txtIdToSelect" runat="server"></asp:TextBox><br />
54

<asp:Button ID="btnSelect" runat="server" Text="Select" OnClick="btnSelect_Click" /><br />
55

<asp:Label ID="lblData" runat="server" Text=""></asp:Label>
56

</div>
57

</form>
58

</body>
59

</html>

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原文地址：https://www.cnblogs.com/wenjie/p/1164052.html