windows窗体中 与数据库连接的代码要怎么写比较好，要考虑到窗体很多，要修改连接路径时只要改一处。

不可能每个窗体的连接路径都要改吧！

如果想标准话窗体的话最好是写一个类,进行经常的调用!~
如果现在还没有写类的能力,建议如下:
imports system.data.sqlclient
Dim conn As New SqlConnection("server=.;database=ViBook;integrated security=sspi")
Dim comm As New SqlCommand
Dim ds As New DataSet
Dim da As New SqlDataAdapter
If conn.State = ConnectionState.Closed Then
conn.Open()
End If
comm.Connection = conn
comm.CommandType = CommandType.Text
comm.CommandText = "select 姓名 from 管理员信息"
da.SelectCommand = comm
da.Fill(ds, "图书信息表")
If conn.State = ConnectionState.open Then
conn.close()
End If

相关的表与数据库的连接主键更改就是了
这样写的麻烦之处就是每个窗体都要写入一个连接!

要得就是类的代码和调用的代码，上面的写法不符合要求，要改的话每个窗体都要改了！

可以建一個模塊MODULE呀.
然後在里面定義全局常量呀

还是写类
Imports System
Imports System.Data
Imports System.Data.SqlClient
Public Class class2
Dim str As String = "数据库连接字符串"
Public conn As New SqlConnection(str)
End Class
在类里这样写,然后在 每个页面
friend sqlconnection as new class2
然后就可以直接去调用这个连接了

single，你这样可以吗，不行啊！

在Module1.vb里的：
Imports System.Data.SqlClient
Module Module1
Public ConnString As String = "Data Source=.;Initial Catalog=test;User ID=sa"
Function CreateDataSetaa(ByVal strSQL As String, ByVal TableName As String) As DataSet
Dim objCmd As New SqlDataAdapter(strSQL, ConnString)
Dim DS As New DataSet
objCmd.Fill(DS, TableName)
CreateDataSetaa = DS
End Function
End Module
在Form1.vb里的：
Imports System.Data.SqlClient

Public Class Form1
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
Dim strSql As String = "select * from aaa"
DataGrid1.DataSource = CreateDataSetaa(strSql, "aaa")
Me.DataGrid1.DataMember = "aaa"
End Sub
End Class
但我很想知道 single 你的那种写法！

一个标准的建类方法.比如要建立一个名为database的类,代码编写如下:
Imports System.Data
Imports System.Data.SqlClient
Imports System.ComponentModel
Public Class DataBase
'实现接口IDisposable
Implements IDisposable
'数据库连接对象
Private SqlConn As SqlConnection
Public Shared sConn As String = "Persist Security Info=False;Integrated Security=SSPI;database=libbook;server=.;Connect Timeout=30"
Public Sub Dispose() Implements System.IDisposable.Dispose
Dispose(True)
GC.SuppressFinalize(True)
End Sub
Protected Sub Dispose(ByVal disposing As Boolean)
If disposing <> True Then
Return
End If

If SqlConn Is Nothing = False Then
SqlConn.Dispose()
SqlConn = Nothing
End If
End Sub

Public Sub Open()
If SqlConn Is Nothing = True Then
'建立数据库连接对象
SqlConn = New SqlConnection(Me.sConn)
'打开数据库连接
SqlConn.Open()
End If
End Sub
Public Sub Close()
'如果数据库连接对象不为空则关闭数据库连接
If SqlConn Is Nothing = False Then
SqlConn.Close()
End If
End Sub
Public Function RunSelectSQL(ByVal sSQLString As System.String) As DataView
Me.Open()
Dim SqlDS As DataSet = New DataSet
Dim SqlDA As SqlDataAdapter = New SqlDataAdapter(sSQLString, Me.SqlConn)
SqlDA.Fill(SqlDS)
Return SqlDS.Tables(0).DefaultView
End Function
Public Function RunDelOrInsSQL(ByVal sSQLString As System.String)
Me.Open()
Dim SqlComm As SqlCommand = New SqlCommand(sSQLString, Me.SqlConn)
SqlComm.ExecuteNonQuery()
End Function
End Class