VB.net 的注册页面代码问题！！求帮助

Private Sub Btn_Submit_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Btn_Submit.Click
  Try
  Dim Comstr As String
  '如果是注册一般用户的情况
  If Cmb_Purview.Text.Trim = "一般用户" Then
  '判断两次输入的密码是否一致
  If Txb_Password.Text = Txb_confirmPassword.Text Then
  '将执行的sql语句赋给Comstr
  Comstr = "insert into Tb_" & Cmb_Purview.Text.Trim & "表 values('" & Txb_User.Text.Trim _
  & "','" & CChar(Txb_Password.Text.Trim) & "')"
  '定义sqlcommand 对象
  Dim Mycom As New SqlCommand(Comstr, SqlConnection1)
  '打开数据库连接
  SqlConnection1.Open()
  '执行命令
  Mycom.ExecuteNonQuery()
  '关闭数据库
  SqlConnection1.Close()
  '提示成功注册
  MessageBox.Show("添加成功", "提示", MessageBoxButtons.OK, MessageBoxIcon.Warning)
  Else
  '否则两次密码不相同，将密码置空，并将焦点落在密码文本框
  MessageBox.Show("两次输入密码不相同")
  Txb_Password.Text = ""
  Txb_confirmPassword.Text = ""
  Txb_Password.Focus()

  End If
  Else
  If Txb_Password.Text = Txb_confirmPassword.Text And Txb_SuperPassword.Text = "king" Then
  Comstr = "insert into Tb_" & Cmb_Purview.Text & "表 values('" & _
  Txb_User.Text.Trim & "','" & CChar(Txb_Password.Text.Trim) & "')"
  Dim Mycom As New SqlCommand(Comstr, SqlConnection1)
  SqlConnection1.Open()
  Mycom.ExecuteNonQuery()
  MessageBox.Show("添加成功")
  Else
  MessageBox.Show("密码错误 ！！")
  Txb_Password.Text = ""
  Txb_confirmPassword.Text = ""
  Txb_SuperPassword.Text = ""
  Txb_Password.Focus()

  End If
  End If
  Catch ex As Exception
  MessageBox.Show("该用户名已被注册，请选另一个用户名！！！")
  Txb_User.Text = ""
  Txb_Password.Text = ""
  Txb_confirmPassword.Text = ""
  Txb_User.Focus()
  Finally
  SqlConnection1.Close()
  End Try
  End Sub


不知道为什么总是执行Catch 语句！！

搞好了，是sql语句的问题，中文输入法与英文输入法的差别啊