Private Sub Button_login_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button_login.Click
If TextBox_user.Text.Trim = "" Then
MsgBox("用户名不能为空!", MsgBoxStyle.Critical, "错误")
TextBox_user.Focus()
Exit Sub
End If
If TextBox_pwd.Text.Trim = "" Then
MsgBox("密码不能为空!", MsgBoxStyle.Critical, "错误")
TextBox_pwd.Focus()
Exit Sub
End If
Dim sql As String
Dim myconn As Odbc.OdbcConnection = New Odbc.OdbcConnection
myconn.ConnectionString = odbcProductString
Dim mycomm As Odbc.OdbcCommand = New Odbc.OdbcCommand
mycomm.Connection = myconn
Dim myreader As Odbc.OdbcDataReader
Try
sql = "select 用户名,真实姓名,密码 from 用户基本信息表 where 用户名='" + TextBox_user.Text.Trim + "' and 密码='" + TextBox_pwd.Text.Trim + "'"
mycomm.CommandText = sql
myconn.Open()
myreader = mycomm.ExecuteReader
If myreader.Read() = True Then
User = myreader("用户名")
ElseIf Not myreader.HasRows Then
MsgBox("用户名或密码错!", MsgBoxStyle.Critical, "错误")
Exit Sub
End If
myreader.Read()
当前用户 = myreader.GetString(0).Trim
当前用户姓名 = myreader.GetString(1).Trim
用户密码 = myreader.GetString(2).Trim
Me.Hide()
主窗体对象.ShowDialog()
'显示主窗体
Catch ex As Exception
MsgBox(ex.Message, MsgBoxStyle.Critical)
End Try
End Sub

其中
If myreader.Read() = True Then
User = myreader("用户名")
ElseIf Not myreader.HasRows Then
MsgBox("用户名或密码错!", MsgBoxStyle.Critical, "错误")
Exit Sub
End If
是想实现当用户名密码正确时，把用户名赋值给变量user用来以后调用当前用户ID
可是现在登陆后会出现提示“不存在此行/列的数据”
要怎么解决？？

唔，解决了- -
把后面改成
While (myreader.Read())
当前用户 = myreader.GetString(0).Trim
当前用户姓名 = myreader.GetString(1).Trim
用户密码 = myreader.GetString(2).Trim
End While