如何向OnChangeEventHandler添加參數

Question

我需要爲插入數據庫的不同「符號」行設置不同的SqlDependencies。

如何在OnChangeEventHandler設置中傳遞Symbol？

public void SetDepedencyForSymbol(string symbol) 
{ 
    string cmdText = "SELECT [Symbol] FROM [" + AccountCode + "].[FilledOrders] WHERE [Symbol] = '" + symbol + "'"; 
    using (SqlCommand command = new SqlCommand(cmdText, conn)) 
    { 

     SqlDependency FilledDependency = new SqlDependency(command); 
     FilledDependency.OnChange += new OnChangeEventHandler(OnDependencyForFillsChange); 

     using (SqlDataReader reader = command.ExecuteReader()) 
     { 
      // Process the DataReader. 
     } 
    } 
} 

void OnDependencyForFillsChange(object sender, SqlNotificationEventArgs e) 
{ 
    // Handle the event (for example, invalidate this cache entry). 

    // How can I get value of "symbol" here 
} 

Answer 1

您不能更改事件處理程序的簽名。 SqlDependency的OnChange事件的處理程序將始終接受object和SqlNotificationEventArgs，您無法更改此設置。

儘管您可以使用匿名委託來處理事件。然後你將能夠訪問符號參數：

public void SetDepedencyForSymbol(string symbol) 
{ 
    string cmdText = "SELECT [Symbol] FROM [" + AccountCode + "].[FilledOrders] WHERE [Symbol] = '" + symbol + "'"; 

    OnChangeEventHandler handler = (sender, args) => 
    { 
     string theSymbol = symbol; 
     // Handle the event (for example, invalidate this cache entry). 

    }; 
    using (SqlCommand command = new SqlCommand(cmdText, conn)) 
    { 

     SqlDependency FilledDependency = new SqlDependency(command); 
     FilledDependency.OnChange += handler; 

     using (SqlDataReader reader = command.ExecuteReader()) 
     { 
      // Process the DataReader. 
     } 
    } 
}