内单和委托C＃非同步SQL [英] C# asynch SQL inside singleton and delegates
问题描述
我试图建立一个类，将负责对数据库中的所有操作。
从这里使用Singleton模式：<一href=\"http://$c$cbender.denniland.com/a-singleton-base-class-to-implement-the-singleton-pattern-in-c/\" rel=\"nofollow\">http://$c$cbender.denniland.com/a-singleton-base-class-to-implement-the-singleton-pattern-in-c/
我已经建立像这样的类：
类DB：SingletonBase＆LT;＆DB GT;
{ 公共静态只读字符串SqlConnectionString = @数据源= MYDB;初始目录=产品;集成安全性= TRUE;异步处理=真;; 私人DB（）
{
} 公共无效loadData（）
{
康涅狄格州的SqlConnection =新的SqlConnection（SqlConnectionString）;
的SqlCommand CMD = conn.CreateCommand（）;
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText =STATISTICS_1; cmd.Connection =康恩;
conn.Open（）;
IAsyncResult的结果= cmd.BeginExecuteReader（新的AsyncCallback（HandleCallback），CMD，CommandBehavior.CloseConnection）;
} 私人无效HandleCallback（IAsyncResult的结果）
{
SqlDataReader的博士;
的SqlCommand _this =（的SqlCommand）result.AsyncState; 如果（result.IsCompleted）
{
博士= _this.EndExecuteReader（结果）;
}
其他
博士= NULL; DataTable的DT =新的DataTable（）;
dt.Load（DR）;
dr.Close（）;
MessageBox.Show（装）;
}
}
在我的主类，我用这个像这样：
私人无效loadStatistics（对象发件人，EventArgs的发送）
{
showStatus（加载数据）;
DB.Instance.loadData（）;
}
但是，这会给我只有我的消息框。
我想这样做是我，将SQL查询返回的东西后调用主类声明的功能。
我认为最好的办法就是用事件，但我不知道该怎么做适当的方式。
我愿做这样的事情在我的主类：
私人无效loadCompleted（string信息）
{
MessageBox.Show（MSG）;
} 私人无效loadStatistics（对象发件人，EventArgs的发送）
{
showStatus（加载数据）;
DB.Instance.loadData（loadCompleted）;
}
所以，我可以指定函数，将SQL调用完成后调用。
我不知道这是不是这样做的最佳方式，因此任何意见，建议和解决方案都欢迎。
我想实现是有负责调用SQL和异步数据传递给将处理它的其它功能类。
公共委托无效NotifyCallback（字符串消息）;公共类ClassWithCommandAndCallback
{
公众的SqlCommand的Sql;
公共NotifyCallback回调;
}公共无效loadData（NotifyCallback回调）
{
ClassWithCommandAndCallback AR =新ClassWithCommandAndCallback（）;
ar.Sql = CMD;
ar.Callback =回调;
IAsyncResult的结果= cmd.BeginExecuteReader（新的AsyncCallback（HandleCallback），AR，CommandBehavior.CloseConnection）;
}私人无效HandleCallback（IAsyncResult的结果）
{
ClassWithCommandAndCallback AR =（ClassWithCommandAndCallback）result.AsyncState; ar.Callback（装（SQL是：+ ar.Sql +））;
}
I'm trying to build a class that will be responsible for all operations on database.
Using singleton pattern from here: http://codebender.denniland.com/a-singleton-base-class-to-implement-the-singleton-pattern-in-c/
I've build a class like so:
class DB : SingletonBase<DB>
{
public static readonly string SqlConnectionString = @"Data Source=MYDB;Initial Catalog=PRODUCTS;Integrated Security=True;Asynchronous Processing=true;";
private DB()
{
}
public void loadData()
{
SqlConnection conn = new SqlConnection(SqlConnectionString);
SqlCommand cmd = conn.CreateCommand();
cmd.CommandType = CommandType.StoredProcedure;
cmd.CommandText = "STATISTICS_1";
cmd.Connection = conn;
conn.Open();
IAsyncResult result = cmd.BeginExecuteReader(new AsyncCallback(HandleCallback), cmd, CommandBehavior.CloseConnection);
}
private void HandleCallback(IAsyncResult result)
{
SqlDataReader dr;
SqlCommand _this = (SqlCommand)result.AsyncState;
if (result.IsCompleted)
{
dr = _this.EndExecuteReader(result);
}
else
dr = null;
DataTable dt = new DataTable();
dt.Load(dr);
dr.Close();
MessageBox.Show("loaded");
}
}
In my main class I'm using this like so:
private void loadStatistics(object sender, EventArgs e)
{
showStatus("loading data");
DB.Instance.loadData();
}
But this will give me only my message box.
What I would like to do is to declare function in my main class that will be called after SQL query return something.
I think that the best way would by using events, but I don't know how to do that proper way.
I would like to do something like this in my main class:
private void loadCompleted(string msg)
{
MessageBox.Show(msg);
}
private void loadStatistics(object sender, EventArgs e)
{
showStatus("loading data");
DB.Instance.loadData(loadCompleted);
}
So that I can specify function that will be called after SQL call is finished.
I don't know if this is the best way of doing this, so any comments, suggestions and solutions are welcome.
What I would like to achieve is to have one class responsible for calling SQL asynchronously and passing data to other functions that will process it.
public delegate void NotifyCallback(string message);
public class ClassWithCommandAndCallback
{
public SqlCommand Sql;
public NotifyCallback Callback;
}
public void loadData(NotifyCallback callback)
{
ClassWithCommandAndCallback ar = new ClassWithCommandAndCallback();
ar.Sql = cmd;
ar.Callback = callback;
IAsyncResult result = cmd.BeginExecuteReader(new AsyncCallback(HandleCallback), ar, CommandBehavior.CloseConnection);
}
private void HandleCallback(IAsyncResult result)
{
ClassWithCommandAndCallback ar = (ClassWithCommandAndCallback)result.AsyncState;
ar.Callback("loaded (SQL was: "+ar.Sql+")");
}
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