vb.net登录界面警告 vb登录界面设计代码

VB.NET中出现如图所示的警告如何更正，帮忙解决下 谢谢

Private Function getAccessConnection() As OleDbConnection

'整体思路应该是：连接数据库－运用适配器运行查询词句-将查询结果填充到数据集－以数据集为数据源，在DataGrid中显示。

Dim dbConnectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0;

Data Source=|DataDirectory|\Resources\mag.mdb;Persist Security Info=true"

'连接字符串，Provider,连接引擎，可以死记，OLEDB就用这处，Data Source,设置数据库的位置。

Dim dbConnection As OleDbConnection = New OleDbConnection(dbConnectionString)

Try

dbConnection.Open()

Catch Ex As Exception

’MsgBox(Err.Description)

End Try

Return dbConnection

End Function

private Sub fillDataGridView()

Dim sqlStr As String = "select * from Table"

Dim DataAdapter As New OleDbDataAdapter

Dim dataSet As New DataSet

Dim DataGridView As New DataGridView

Dim dbConnection As OleDbConnection = getAccessConnection()

If dbConnection.State.ToString = "Closed" Then

MsgBox(Chr(13) " access 数据库连接失败 " Chr(13), , "警告")

Exit Sub

End If

DataAdapter.SelectCommand = New OleDbCommand(sqlStr,dbConnection)

'用数据适配器进行查询

Try

DataAdapter.Fill(dataSet,"Table") '将查询结果填充到数据集Dataset,有点像VB中的记录集recordset

DataGridView.DataSource = dataSet.Tables("Table").DefaultView '将数据集的内容在表格中显示出来

Catch Ex As Exception

MsgBox(Err.Description)

Finally

dataSet.Dispose

DataAdapter.Dispose

dbConnection.Close

dbConnection.Dispose

End Try

End Sub

相关问答

Q1: VB.NET2005连接数据库做登录界面出错，变量MsgText在赋值前被使用，可能会在运行时导致空引用，高手来！

可以不用管它，因为默认值是空，想不出现警告就定义成：dim MsgText as string=""

Q2: 在VB.NET中做登陆界面老是出现这个错误

oledbconnection conn=new oledbconnection("连接字符串")

conn.open()

oledbcommand1.connection=conn;

oledb.comandtext= "SELECT 用户, 密码 FROM yonghu where 用户='" Me.TextBox1.Text "' and 密码='" Me.TextBox2.Text "'"

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