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C#教程之c#异步读取数据库与异步更新ui的代码实
异步读取数据库,在数据绑定的时候会出现点问题,就是窗体界面会无法关闭,要结束任务才能结束进程。例如下面代码
首先按习惯的方法，设定线程更新UI
a2.CheckForIllegalCrossThreadCalls = false; //a2为窗体名称
下面的代码就是从数据库里取得数据并绑定
private void button1_Click(object sender, EventArgs e)
{
SqlConnection con;
SqlCommand com;
try
{
con = new SqlConnection("UID=sa;Password=123;Initial Catalog=AD;Data Source=192.168.1.1;Asynchronous Processing=true");
con.Open();
com = new SqlCommand("select top 100 * from tb_user", con);
com.BeginExecuteReader(new AsyncCallback(delDataBin), com);
}
catch (Exception ex)
{
MessageBox.Show("程序发生错误,信息: " + ex.Message);
}
}
private void delDataBin(IAsyncResult ar)
{
if (ar.IsCompleted)
{
SqlCommand com = (SqlCommand)ar.AsyncState;
SqlDataReader dr = com.EndExecuteReader(ar);
DataTable dt = new DataTable();
dt.Load(dr);
dr.Close();
this.dataGridView1.DataSource = dt; //绑定数据
}
}
到这里完成的绑定的工作，运行查看一下效果，其实这样是会出现窗体假死的现象。
下面通过Invoke 来实现
首先声明委托 public delegate void updateDG(DataTable dt);
然后通过dataBin来绑定DataGridView
public void dataBin(DataTable dt)
{
dataGridView1.DataSource = dt;
return;
}
在线程里面调用下面方法
//绑定数据
if (this.InvokeRequired)
{
updateDG ur = new updateDG(dataBin);
this.Invoke(ur, dt);
}
完整的代码如下:
private void button1_Click(object sender, EventArgs e)
{
SqlConnection con;
SqlCommand com;
try
{
con = new SqlConnection("UID=sa;Password=123;Initial Catalog=AD;Data Source=192.168.1.1;Asynchronous Processing=true");
con.Open();
com = new SqlCommand("select top 100 * from tb_user", con);
com.BeginExecuteReader(new AsyncCallback(delDataBin), com);
}
catch (Exception ex)
{
MessageBox.Show("程序发生错误,信息: " + ex.Message);
}
}
private void delDataBin(IAsyncResult ar)
{
if (ar.IsCompleted)
{
SqlCommand com = (SqlCommand)ar.AsyncState;
SqlDataReader dr = com.EndExecuteReader(ar);
DataTable dt = new DataTable();
dt.Load(dr);
dr.Close();
//this.dataGridView1.DataSource = dt;//绑定数据
if (this.InvokeRequired)
{
updateDG ur = new updateDG(dataBin);
this.Invoke(ur, dt);
}
}
}
public delegate void updateDG(DataTable dt);
public void dataBin(DataTable dt)
{
dataGridView1.DataSource = dt;
return;
}
查运行查看一下，你就会发现结果了
