asp.net中SqlCacheDependency缓存技术概述

下面是详细讲解“asp.net中SqlCacheDependency缓存技术概述”的完整攻略。

什么是SqlCacheDependency缓存技术

在ASP.NET中，我们通常使用缓存技术来提高网站的访问速度和性能。SqlCacheDependency缓存技术是ASP.NET提供的一种高级缓存技术。它通过监视SQL Server数据库的表或视图上所做的更改来自动使ASP.NET缓存无效，从而保持缓存的有效性和及时性。

如何使用SqlCacheDependency缓存技术

使用SqlCacheDependency缓存技术有以下几个步骤：

启用缓存依赖
在Web.config文件中，需要添加以下行来启用缓存依赖：

<caching>
  <cache disableMemoryCollection="true" />
</caching>
<system.web>
  <caching>
    <sqlCacheDependency enabled="true" />
  </caching>
</system.web>

设置enabled属性为true，这将启用缓存依赖。

配置缓存依赖
在Web.config文件中，需要配置SQL Server数据库连接字符串和缓存依赖项。例如：

<connectionStrings>
  <add name="ConnectionString" connectionString="Data Source=.\SQLExpress;Initial Catalog=MyDB;Integrated Security=True" providerName="System.Data.SqlClient"/>
</connectionStrings>

<system.web>
  <caching>
    <sqlCacheDependency enabled="true">
      <databases>
        <add name="MyDB" connectionStringName="ConnectionString" pollTime="10:00:00" />
      </databases>
    </sqlCacheDependency>
  </caching>
</system.web>

添加databases元素并设置name为所要监视的数据库名称，connectionStringName为连接字符串名称，pollTime为轮询数据库的时间间隔。

在ASP.NET中使用缓存依赖
在ASP.NET代码中使用SqlCacheDependency缓存技术的方法和常规缓存技术一样。例如，使用缓存技术获取商品列表的代码：

public List<Product> GetProductList()
{
    string cacheKey = "productList";
    List<Product> products = (List<Product>)HttpContext.Current.Cache[cacheKey];
    if (products == null)
    {
        products = LoadProductListFromDatabase();
        HttpContext.Current.Cache.Insert(cacheKey, products, null, 
            DateTime.Now.AddMinutes(30), Cache.NoSlidingExpiration,
            CacheItemPriority.Default, OnProductListRemove);
    }
    return products;
}

在这里，我们使用HttpContext.Current.Cache对象来获取和设置缓存。当缓存依赖项更改时，需要调用OnProductListRemove方法来使缓存无效：

private void OnProductListRemove(string key, object value, CacheItemRemovedReason reason)
{
    if (reason == CacheItemRemovedReason.DependencyChanged)
    {
        SqlCacheDependencyAdmin.EnableNotifications("MyDB");
        SqlCacheDependencyAdmin.EnableTableForNotifications("MyDB", "Product");
    }
}

在这里，我们使用SqlCacheDependencyAdmin类来启用依赖项更改通知。EnableNotifications方法启用对指定数据库的通知，EnableTableForNotifications方法启用对指定表或视图的通知。

在SQL Server数据库中启用缓存依赖
在SQL Server数据库中，需要启用缓存依赖并创建缓存依赖项。例如，要在Product表上启用缓存依赖项，可以执行以下SQL语句：

EXECUTE sp_configure 'show advanced options', 1;
RECONFIGURE WITH OVERRIDE;
EXECUTE sp_configure 'clr enabled', 1;
RECONFIGURE WITH OVERRIDE;
GO
CREATE ASSEMBLY [System.Web] FROM 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\System.Web.dll' WITH PERMISSION_SET = UNSAFE;  --这个路径可能因为操作系统和.net版本等原因会不同
GO
CREATE ASSEMBLY [SqlCacheDependencyImp] AUTHORIZATION [dbo]
FROM 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\SqlCacheDependency.dll';  --这个路径可能因为操作系统和.net版本等原因会不同
GO
CREATE TABLE [dbo].[Product](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NOT NULL,
    [Category] [nvarchar](50) NOT NULL,
    [Price] [decimal](18, 2) NOT NULL,
    CONSTRAINT [PK_Product] PRIMARY KEY CLUSTERED ([Id] ASC)
);
GO
EXEC sys.sp_addapprole 'productrole', 'productpassword';
GO
CREATE PROCEDURE [dbo].[ProductInsert]
    @Name NVARCHAR(50),
    @Category NVARCHAR(50),
    @Price DECIMAL(18,2)
AS
BEGIN
    SET NOCOUNT ON;

    INSERT INTO [dbo].[Product] ([Name], [Category], [Price])
    VALUES (@Name, @Category, @Price);
END
GO
EXEC sp_addrolemember 'productrole', 'sa';
GRANT EXECUTE ON [dbo].[ProductInsert] TO [productrole];
GO
EXEC sp_changedbowner 'sa';
GO
EXEC sp_configure 'Database Mail XPs', 1;
RECONFIGURE WITH OVERRIDE;
GO
EXEC sp_addmessage 14660, 16, N'Product Inserted.', N'dbo';
GO
EXEC sp_addmessage 14661, 16, N'Another Product Inserted.', N'dbo';
GO
CREATE TRIGGER [ProductInsertTrigger] ON [dbo].[Product]
AFTER INSERT
AS
BEGIN
    SET NOCOUNT ON;

    DECLARE @ProductId INT;
    SELECT @ProductId = [Id] FROM INSERTED;

    DECLARE @MessageBody NVARCHAR(200);
    SET @MessageBody = 'Product Inserted. Product ID: ' + CONVERT(NVARCHAR(20), @ProductId);
    EXEC msdb.dbo.sp_send_dbmail
        @recipients='your_email_address@example.com',
        @subject='Product Inserted.',
        @body=@MessageBody;

    RAISERROR (14660, 16, 1);
END
GO
EXEC sp_configure 'show advanced options', 0;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'clr enabled', 0;
RECONFIGURE WITH OVERRIDE;

在这里，我们创建了Product表并启用了缓存依赖项。当在Product表中插入一条新记录时，将自动通知ASP.NET缓存使缓存无效。

示例：启用SqlCacheDependency缓存技术

以下是示例代码，演示如何在Web应用程序中使用SqlCacheDependency缓存技术：

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindData();
        StartSqlDependency();
    }
}

private void BindData()
{
    string cacheKey = "productList";
    List<Product> products = (List<Product>)HttpContext.Current.Cache[cacheKey];
    if (products == null)
    {
        products = LoadProductListFromDatabase();
        HttpContext.Current.Cache.Insert(cacheKey, products, null, 
            DateTime.Now.AddMinutes(30), Cache.NoSlidingExpiration,
            CacheItemPriority.Default, OnProductListRemove);
    }
    GridView1.DataSource = products;
    GridView1.DataBind();
}

private void OnProductListRemove(string key, object value, CacheItemRemovedReason reason)
{
    if (reason == CacheItemRemovedReason.DependencyChanged)
    {
        SqlCacheDependencyAdmin.EnableNotifications("MyDB");
        SqlCacheDependencyAdmin.EnableTableForNotifications("MyDB", "Product");
    }
}

private void StartSqlDependency()
{
    using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
    using (SqlCommand command = new SqlCommand("SELECT [Id], [Name], [Category], [Price] FROM [dbo].[Product] ORDER BY [Id]", connection))
    {
        connection.Open();
        SqlCacheDependency dependency = new SqlCacheDependency(command);
        command.CommandType = CommandType.Text;
        command.Notification = null;
        command.CommandTimeout = 15;
        Cache.Insert("dependency", dependency, null, 
            Cache.NoAbsoluteExpiration, Cache.NoSlidingExpiration, 
            CacheItemPriority.NotRemovable, OnDependencyRemove);
        command.ExecuteReader();
    }
}

private void OnDependencyRemove(string key, object value, CacheItemRemovedReason reason)
{
    if (reason == CacheItemRemovedReason.DependencyChanged)
    {
        BindData();
        StartSqlDependency();
    }
}

private List<Product> LoadProductListFromDatabase()
{
    List<Product> productList = new List<Product>();
    using (SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ConnectionString))
    using (SqlCommand command = new SqlCommand("SELECT [Id], [Name], [Category], [Price] FROM [dbo].[Product] ORDER BY [Id]", connection))
    {
        connection.Open();
        using (SqlDataReader reader = command.ExecuteReader())
        {
            while (reader.Read())
            {
                productList.Add(new Product {
                    Id = reader.GetInt32(0),
                    Name = reader.GetString(1),
                    Category = reader.GetString(2),
                    Price = reader.GetDecimal(3)
                });
            }
        }
    }
    return productList;
}

在这个示例中，我们使用SqlCacheDependency缓存技术来缓存Product列表。当在Product表中插入、更新或删除记录时，将自动通知ASP.NET缓存使缓存无效。

示例：在SQL Server中启用缓存依赖

以下是示例SQL脚本，演示如何在SQL Server中启用缓存依赖：

EXEC sp_configure 'show advanced options', 1;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'clr enabled', 1;
RECONFIGURE WITH OVERRIDE;
GO
CREATE ASSEMBLY [System.Web] FROM 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\System.Web.dll' WITH PERMISSION_SET = UNSAFE;
GO
CREATE ASSEMBLY [SqlCacheDependencyImp] AUTHORIZATION [dbo]
FROM 'C:\Windows\Microsoft.NET\Framework64\v4.0.30319\SqlCacheDependency.dll';
GO
CREATE TABLE [dbo].[Product](
    [Id] [int] IDENTITY(1,1) NOT NULL,
    [Name] [nvarchar](50) NOT NULL,
    [Category] [nvarchar](50) NOT NULL,
    [Price] [decimal](18, 2) NOT NULL,
    CONSTRAINT [PK_Product] PRIMARY KEY CLUSTERED ([Id] ASC)
);
GO
EXEC sys.sp_addapprole 'productrole', 'productpassword';
GO
CREATE PROCEDURE [dbo].[ProductInsert]
    @Name NVARCHAR(50),
    @Category NVARCHAR(50),
    @Price DECIMAL(18,2)
AS
BEGIN
    SET NOCOUNT ON;

    INSERT INTO [dbo].[Product] ([Name], [Category], [Price])
    VALUES (@Name, @Category, @Price);
END
GO
EXEC sp_addrolemember 'productrole', 'sa';
GRANT EXECUTE ON [dbo].[ProductInsert] TO [productrole];
GO
EXEC sp_changedbowner 'sa';
GO
EXEC sp_configure 'Database Mail XPs', 1;
RECONFIGURE WITH OVERRIDE;
GO
EXEC sp_addmessage 14660, 16, N'Product Inserted.', N'dbo';
GO
EXEC sp_addmessage 14661, 16, N'Another Product Inserted.', N'dbo';
GO
CREATE TRIGGER [ProductInsertTrigger] ON [dbo].[Product]
AFTER INSERT
AS
BEGIN
    SET NOCOUNT ON;

    DECLARE @ProductId INT;
    SELECT @ProductId = [Id] FROM INSERTED;

    DECLARE @MessageBody NVARCHAR(200);
    SET @MessageBody = 'Product Inserted. Product ID: ' + CONVERT(NVARCHAR(20), @ProductId);
    EXEC msdb.dbo.sp_send_dbmail
        @recipients='your_email_address@example.com',
        @subject='Product Inserted.',
        @body=@MessageBody;

    RAISERROR (14660, 16, 1);
END
GO
EXEC sp_configure 'show advanced options', 0;
RECONFIGURE WITH OVERRIDE;
EXEC sp_configure 'clr enabled', 0;
RECONFIGURE WITH OVERRIDE;

在这个示例中，我们创建了Product表并启用了缓存依赖项。当在Product表中插入一条新记录时，将自动通知ASP.NET缓存使缓存无效。同时，我们还添加了一个触发器，当有新的Product记录插入时，将发送电子邮件通知。

本站文章如无特殊说明，均为本站原创，如若转载，请注明出处：asp.net中SqlCacheDependency缓存技术概述 - Python技术站

asp.net中SqlCacheDependency缓存技术概述

什么是SqlCacheDependency缓存技术

如何使用SqlCacheDependency缓存技术

示例：启用SqlCacheDependency缓存技术

示例：在SQL Server中启用缓存依赖

相关文章