Imports System.Data
Imports System.Data.SqlClient
Public Class Form8
    Private connstr As String = "Server=(local);packet size=4096;Database=testwater;User ID=sa;Password=;Trusted_Connection=False"
    Private Conn As New SqlConnection(connstr)
    Public sql As String
    Private Sub Form8_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        If sql = "" Then
            sql = "select * from [test] order by id asc"
        End If
        l(sql)
    End Sub

    Private Sub l(ByVal sql As String)
        ' Dim sql As String = "select * from [test] order by id asc"
        Dim cmd As New SqlDataAdapter(sql, Conn)
        Dim ds As New DataSet
        cmd.Fill(ds, "工")
        MsgBox(ds.Tables("工").Rows.Count)
    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Dim c As New Form9
        c.ShowDialog()
        If c.DialogResult = Windows.Forms.DialogResult.OK Then
            sql = c.TextBox1.Text.Trim
        End If
        l(sql)
    End Sub
End Class

Public Class Form9

    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        DialogResult = Windows.Forms.DialogResult.OK
    End Sub
End Class

        //父窗口有关代码
        vehicle.vehicleOutDetailForm outForm = new vehicleOutDetailForm();
        outForm.RaiseVehicleChangedEvent += new EventHandler<VehicleChangEventArgs>(outForm_RaiseVehicleChangedEvent);
        outForm.ViewMode = vehicleOutDetailForm.VehicleOutFormViewMode.AddNew;
        outForm.ShowDialog();

        void outForm_RaiseVehicleChangedEvent(object sender, VehicleChangEventArgs e)
        {
            RefreshList();
        }
        
    //子窗口中定义事件，为了扩展需要即使不传递参数还是尽量声明一个自定义事件参数类
     public class VehicleChangEventArgs : EventArgs
    {
        public VehicleChangEventArgs(string vehicleNo)
        {
            this.vehicleNo = vehicleNo;
        }
        private string vehicleNo;
        public string VehicleNo
        {
            get { return vehicleNo; }
        }
    }

    public event EventHandler<VehicleChangEventArgs> RaiseVehicleChangedEvent;

    //在保存按钮中可用此函数激发事件，如OnRaiseVehicleChangedEvent(new VehicleChangEventArgs(""));
    protected virtual void OnRaiseVehicleChangedEvent(VehicleChangEventArgs e)
    {
        EventHandler<VehicleChangEventArgs> handler = this.RaiseVehicleChangedEvent;
        if (handler !=null)
        {
            handler(this, e);
        }
    }