【发布时间】：2021-03-22 13:27:55
【问题描述】：
我有一个使用 SqlDependency 的 Windows 应用程序。此应用程序表示一个日志监视器 UI，获取数据库中特定表中添加的最新行并在 DataGridView 中查看 代码实现了 SQL Server 中的更改，但 DataGridView 没有显示（没有错误，也没有数据，与数据表中的行一样多）
这是我的代码
public partial class Form1 : Form
{
private int changeCount = 0;
private const string tableName = "NhanVien";
private const string statusMessage = "Đã có {0} thay đổi.";
//' The following objects are reused
//' for the lifetime of the application.
private SqlConnection connection = null;
private SqlCommand command = null;
private DataSet dataToWatch = null;
public Form1()
{
InitializeComponent();
Form2 frm = new Form2();
frm.Show();
}
private bool CanRequestNotifications()
{
// In order to use the callback feature of the
// SqlDependency, the application must have
// the SqlClientPermission permission.
try
{
SqlClientPermission perm = new SqlClientPermission(PermissionState.Unrestricted);
perm.Demand();
return true;
}
catch (Exception ex)
{
return false;
}
}
private string GetConnectionString()
{
// To avoid storing the connection string in your code,
// you can retrive it from a configuration file.
// Return "Data Source=THU-PC\TINTIN;Initial Catalog=QLVT;Persist Security Info=True;User ID=sa;Password=kc;Pooling = false"
return "Data Source=MSI;Initial Catalog=ChuyenDeCNPM;User ID=sa;Password=123;";
}
private string GetSQL()
{
return "select manv as [Mã NV],Ho as [ Họ],Ten as [Tên],phai as [Phái],diachi as [ Địa chỉ] from dbo.NhanVien";
}
private void nhanVienBindingNavigatorSaveItem_Click(object sender, EventArgs e)
{
this.Validate();
this.nhanVienBindingSource.EndEdit();
this.tableAdapterManager.UpdateAll(this.chuyenDeCNPMDataSet);
}
private void Form1_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'chuyenDeCNPMDataSet.NhanVien' table. You can move, or remove it, as needed.
//this.nhanVienTableAdapter.Fill(this.chuyenDeCNPMDataSet.NhanVien);
if (CanRequestNotifications() == true)
BatDau();
else
MessageBox.Show("Bạn chưa kích hoạt dịch vụ Broker", "Cảnh báo", MessageBoxButtons.OK);
}
private void dependency_OnChange(object sender, SqlNotificationEventArgs e)
{
// This event will occur on a thread pool thread.
// It is illegal to update the UI from a worker thread
// The following code checks to see if it is safe update the UI.
ISynchronizeInvoke i = (ISynchronizeInvoke)this;
// If InvokeRequired returns True, the code is executing on a worker thread.
if (i.InvokeRequired)
{
// Create a delegate to perform the thread switch
OnChangeEventHandler tempDelegate = new OnChangeEventHandler(dependency_OnChange);
object[] args = new[] { sender, e };
// Marshal the data from the worker thread
// to the UI thread.
i.BeginInvoke(tempDelegate, args);
return;
}
// Remove the handler since it's only good
// for a single notification
SqlDependency dependency = (SqlDependency)sender;
dependency.OnChange -= dependency_OnChange;
// At this point, the code is executing on the
// UI thread, so it is safe to update the UI.
++changeCount;
this.label1.Text = string.Format(statusMessage, changeCount);
// Add information from the event arguments to the list box
// for debugging purposes only.
{
var withBlock = this.ListBox1.Items;
withBlock.Clear();
withBlock.Add("Info: " + e.Info.ToString());
withBlock.Add("Source: " + e.Source.ToString());
withBlock.Add("Type: " + e.Type.ToString());
}
// Reload the dataset that's bound to the grid.
GetData();
}
private void GetData()
{
// Empty the dataset so that there is only
// one batch worth of data displayed.
dataToWatch.Clear();
// Make sure the command object does not already have
// a notification object associated with it.
command.Notification = null;
// Create and bind the SqlDependency object
// to the command object.
SqlDependency dependency = new SqlDependency(command);
dependency.OnChange += new OnChangeEventHandler(dependency_OnChange);
using (SqlDataAdapter adapter = new SqlDataAdapter(command))
{
adapter.Fill(dataToWatch, tableName);
DataGridView1.DataSource = null;
DataGridView1.DataSource = dataToWatch;
DataGridView1.DataMember = tableName;
}
/*DataTable dt = new DataTable();
dt.Load(command.ExecuteReader(CommandBehavior.CloseConnection));
DataGridView1.DataSource = dt;*/
}
private void BatDau()
{
changeCount = 0;
// Remove any existing dependency connection, then create a new one.
SqlDependency.Stop(GetConnectionString());
try
{
SqlDependency.Start(GetConnectionString());
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return;
}
if (connection == null)
{
connection = new SqlConnection(GetConnectionString());
connection.Open();
}
if (command == null)
// GetSQL is a local procedure that returns
// a paramaterized SQL string. You might want
// to use a stored procedure in your application.
command = new SqlCommand(GetSQL(), connection);
if (dataToWatch == null)
dataToWatch = new DataSet();
GetData();
}
private void button_update_Click(object sender, EventArgs e)
{
Update form = new Update();
form.Show();
}
private void Form1_FormClosed(System.Object sender, System.Windows.Forms.FormClosedEventArgs e)
{
SqlDependency.Stop(GetConnectionString());
if (connection != null)
connection.Close();
}
private void DataGridView1_CellContentClick(object sender, DataGridViewCellEventArgs e)
{
}
private void button_exit_Click(object sender, EventArgs e)
{
this.Close();
}
}
}
【问题讨论】：
标签： c# datagridview dependencies