用Vb.NET 2010 试着写一个简单的登录窗口，出现以下错误

真不知道怎么回事，这个问题困扰我四五天了，请大神来帮忙！
代码如下：
Imports System.Configuration
Imports System.Data.SqlClient

Public Class Login

Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
Dim nameStr As String = txtName.Text
Dim pwdStr As String = txtPwd.Text
If nameStr = "" Then
MsgBox("用户名不能为空！")
txtName.Focus()
Return
End If
If pwdStr = "" Then
MsgBox("密码不能为空！")
txtPwd.Focus()
Return
End If
Dim connStr As String = ConfigurationManager.ConnectionStrings("MyConnectionString").ConnectionString
Dim conn As SqlConnection = New SqlConnection(connStr)
Dim cmd As SqlCommand = New SqlCommand()
cmd.CommandText = "Select*from UserDetails where username = '" & nameStr & "'"
Dim reader As SqlDataReader
Try
conn.Open()
reader = cmd.ExecuteReader()
If reader.Read() Then
If pwdStr = reader("Pwd") Then
MsgBox("正确的用户和密码")
Else
MsgBox("错误的密码")
End If
Else
MsgBox("没有此用户，请注册后再登陆")
End If
Catch ex As Exception
Throw New ApplicationException(ex.ToString())
Finally
reader.Close()
conn.Close()
End Try
End Sub

Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
txtName.Text = ""
txtPwd.Text = ""
End Sub
End Class


另外还出现这个问题：

我是初学者，对于这样的问题很困惑，大神一定要帮忙啊！