连接Mysql会出现错误，但我也能以其他形式进行 [英] Connecting Mysql Getting Error But I Can Do It In Other Form Also

问题描述

我真的很困惑。我可以在一个Windows应用程序表单中成功连接mysql。但是我在其他窗口中无法做同样的代码!!!!

I am really getting confused. I could connect mysql successfully in one windows application form. But same code I cannot do in other windows form!!!!

Imports MySql.Data
Imports MySql.Data.MySqlClient

Public Class mysqltblinsert
   Dim cont As Mysqlconnnection

   Try

      cont = New MySqlConnection

      cont.ConnectionString = "server=localhost;user id=root;password=xxx;database=mydatabase1;"
      cont.Open()
      Dim str As String = "select * from mydatabase1.tblemp; "
      Dim da As New MySqlDataAdapter("select * from tblemp;", cont)
      Dim ds As New DataSet
      da.Fill(ds, "tblemp")
      cont.Close()
      DGV.DataSource = ds.Tables("tblemp")


   Catch ex As Exception
      MessageBox.Show(ex.Message)

   End Try

End Sub

Error   1   Value of type 'MySql.Data.MySqlClient.MySqlConnection' cannot be converted to 'codeprojects.Mysqlconnnection'.
Error   2   'ConnectionString' is not a member of 'codeprojects.Mysqlconnnection'.
Error   3   'Open' is not a member of 'codeprojects.Mysqlconnnection'
Error   4   Overload resolution failed because no accessible 'New' can be called with these arguments:
    'Public Sub New(selectCommandText As String, selectConnString As String)':

推荐答案

问题在于

Dim cont As Mysqlconnnection

Clue在第一条错误消息中

Clue is in the first error message

Quote：

类型'MySql.Data.MySqlClient.MySqlConnection'的值无法转换为'codeprojects.Mysqlconnnection'

Value of type 'MySql.Data.MySqlClient.MySqlConnection' cannot be converted to 'codeprojects.Mysqlconnnection'

注意字母的大小写。使用

Note the case of the letters. Use

Dim cont As MySqlConnection

所有其他错误（如所列出的）将随之消失。注意 - 通常是这种情况，总是尝试修复报告的第一个问题，然后查看错误列表。

All of the other errors (as listed) will then go away. Note - this is often the case, always attempt to fix the first problem reported and then review the error list.

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