1个解决方案中的2个项目的委托问题 [英] a delegate problem over 2 projects in 1 solution

问题描述

你好朋友，

我有下一个问题.
我有一个项目(DBConnecting.DataObjects.DataObjects)，该项目是Windows窗体应用程序与Sql Server 2008数据库之间的通信.
在我的第二个项目中:一个Windows窗体(引用DBConnecting.DataObjects.DataObjects)，该窗体调用Async表方法以异步加载数据表对象.

Hello Friends,

I have the next problem.
I have a project (DBConnecting.DataObjects.DataObjects) that is the communication between my windows form app and my Sql Server 2008 Database.

In my 2nd project: a Windows form (that references DBConnecting.DataObjects.DataObjects) that calls the Async table method to load a datatable object asynchronous.

string query = "select * from [dbo].[FactInternetSales]";
            DBConnecting.DataObjects.DataObjects.AsyncDataTableStart(query, null, CommandType.Text, null);

在DBConnecting项目中，将调用AsyncDataTableStart，此方法将调用方法GetAsyncDataTableEnd

In the DBConnecting project the AsyncDataTableStart gets called and this method calls the method GetAsyncDataTableEnd

public static IAsyncResult AsyncDataTableStart(String Query, List<sqlparameter> sqlParameters, CommandType sqlCommandType, String ConnectionString)
        {
            SqlCommand command = Open(Query, sqlParameters, sqlCommandType, ConnectionString);
            return command.BeginExecuteReader(GetAsyncDataTableEnd, command, CommandBehavior.CloseConnection);
        }

        public static void GetAsyncDataTableEnd(IAsyncResult myResult)
        {
            SqlCommand command = null;
            SqlDataReader dr = null;
            
            DateTime nu = DateTime.Now;
            DataTable myTable = new DataTable();
            try
            {
                command = (SqlCommand)myResult.AsyncState;
                dr = command.EndExecuteReader(myResult);
                myTable.Load(dr);
                
            }
            catch
            {
            }
            finally
            {
                if (dr != null)
                    dr.Close();
                if (command != null && command.Connection.State != ConnectionState.Closed)
                    command.Connection.Close();
            }
        }
</sqlparameter>

因此，我有一个装载了数据的DataTable对象，但是如何将该表返回到Windowsform?
在DBConnecting.DataObjects.DataObjects类中，我希望有一个委托，当Windows窗体实现此委托时，将返回数据表，以便可以将其设置为DataGridView的数据源.
请通过一些示例帮助我.

So I have a DataTable object loaded with data, but How do I return this table to the windowsform?
In the DBConnecting.DataObjects.DataObjects class I would like to have a delegate that when the windows form implements this delegate the datatable is returned so it can be set as DataSource for a DataGridView.

Please help me with some examples

推荐答案

此 [ ^ ]文章包含有关如何使用IAsyncResult返回信息.

在源项目中创建DataTableEventArgs

This[^] article contains information on how to pass information back using IAsyncResult.

Create the DataTableEventArgs in your source project

public class DataTableEventArgs : System.EventArgs {
    DataTable dataTable;
    public DataTable DataTableInfo {
        get {
            return dataTable;
        }
    }

    public DataTableEventArgs(DataTable dataTable) {
        this.dataTable= dataTable;
    }
}

在源项目中声明委托

Declare the delegate in your source project

public delegate void DataTableEventHandler(object sender, DataTableEventArgs e);

在返回DataTable的类中声明事件

Declare the event in the class that returns the DataTable

public event DataTableEventHandler ReturnDataTable;

引发您要发送DataTable的事件

Raise the event where you want to send the DataTable

if (ReturnDataTable != null) {
    DataTable dataTable = BuildDataTable();
    ReturnDataTable(this, dataTable);
}

现在，在您的接收器类中，该类必须接收DataTable

Now, in your receiver class that must receive the DataTable

private void Init() {
    //Bind your method to the event
    MyDataSource src = new MyDataSource();
    src.ReturnDataTable += new DataTableEventHandler(HandleDataTable);
}

private void HandleDataTable(object sender, DataTableEventArgs e) {
    DataTable dataTable = e.DataTableInfo;
    //Use dataTable here
}

这篇关于1个解决方案中的2个项目的委托问题的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！