Imports System.Data.SqlClient
Public Class Form1
Public blnloginsucc As Boolean
Public Shared connstr As String = "server =jm;database=mydb;uid=sa;pwd=sa"

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim strsql As String = "select * from users where id ='" & cmbid.Text & " 'and pwd= '" & txtpwd.Text & " '"
Dim mycon As New SqlConnection(connstr)
Dim mycom As New SqlCommand(strsql, mycon)
Dim myreader As SqlDataReader
Try
mycon.Open()
myreader = mycom.ExecuteReader
If myreader.Read = True Then
blnloginsucc = True
mycon.Close()
Me.Close()
frmmain.ShowDialog()
Else
MsgBox("密码错误，请重新输入！", MsgBoxStyle.Exclamation)
txtpwd.Focus()
End If
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Exclamation)
End Try
End Sub
End Class

就是运行后，在登录窗口填上用户名和密码后，窗体消失，但主窗体出来闪一下，也消失拉，请高手指点

我试过拉
frmmain.show()
也不行