请各位大神看看为什么连库没反应。代码如下：
Public Class Form4
Dim DS As New DataSet
Dim XSTable As DataTable
Dim Da As New SqlClient.SqlDataAdapter
Public Sub refreshdata()
Da.Update(DS, "st")
XSTable.Clear()
Me.Button1_Click(Nothing, Nothing)
End Sub
Private Sub Button4_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button4.Click
Me.Hide()
Form1.Show()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Me.Hide()
Form6.Show()
End Sub
Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button3.Click
Me.Hide()
Form7.Show()
End Sub
Private Sub Button5_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button5.Click
Dim cn As New SqlClient.SqlConnection
Dim cmd As New SqlClient.SqlCommand
cn.ConnectionString = "server=IDEA-PC\MSSQLSERVER1;uid=hqp;pwd=325314;database=Train_Tickets"
cmd.Connection = cn
Dim builder As SqlClient.SqlCommandBuilder = New SqlClient.SqlCommandBuilder(Da)
cn.Open()
cmd.CommandText = "select * from st"
Da.SelectCommand = cmd
Da.Fill(DS, "st")
XSTable = DS.Tables("st")
cn.Close()
DataGridView1.DataSource = XSTable
End Sub
Private Sub DataGridView1_CellContentClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellContentClick
End Sub
End Class

你是点那个按钮的时候没有反应？Button5的 Click事件吗？

Dim cn As New SqlClient.SqlConnection
Dim cmd As New SqlClient.SqlCommand
cn.ConnectionString = "server=IDEA-PC\MSSQLSERVER1;uid=hqp;pwd=325314;database=Train_Tickets"
cmd.Connection = cn
Dim builder As SqlClient.SqlCommandBuilder = New SqlClient.SqlCommandBuilder(Da)
cn.Open()
cmd.CommandText = "select * from st"
Da.SelectCommand = cmd
Da.Fill(DS, "st")
把这里改为：
Dim cn As New SqlClient.SqlConnection
Dim cmd As New SqlClient.SqlCommand
cn.ConnectionString = "server=IDEA-PC\MSSQLSERVER1;uid=hqp;pwd=325314;database=Train_Tickets"
cn.Open()
cmd.Connection = cn
cmd.CommandType = CommandType.Text
cmd.CommandText = "select * from st"
Dim builder As SqlClient.SqlCommandBuilder = New SqlClient.SqlCommandBuilder()
builder .SelectCommand = cmd
builder .Fill(DS, "st")
这样试试吧。

把对数据库的操作（增加、删除、修改）生成一个类，调用进行操作，那你的这个问题就不存在了。
http://blog.csdn.net/wang19850219/article/details/41440521