各位大佬，我在寫資料庫基礎類，在除錯的時候出現了如截圖的錯誤，不知道該怎么處理，請大佬們指點迷津下，謝謝！
程式如下：
Option Explicit Off
Imports System.Data.SqlClient
#Region "資料庫基本操作類別庫"
Public Class PublicClass
#Region "資料庫連接類"
Public sqlconn As New SqlClient.SqlConnection
Public Sub open_conn()
'Dim sqlconnstr As String
Try
sqlconn.ConnectionString = ("server=127.0.0.1;integrated security=False;Initial Catalog=YNCSys;User ID=sa;Pwd=adminsa226200")
Catch ex As Exception
Throw ex
End Try
End Sub
#End Region
#Region "select 陳述句,需要輸入T-SQL陳述句"
Public Function dataSelect(ByVal strsql As String, ByVal strTableName As String) As DataSet
Dim mydataset As New DataSet
Dim mySqlAdapter As SqlClient.SqlDataAdapter
Try
sqlconn.Open()
mySqlAdapter = New SqlClient.SqlDataAdapter(strsql, sqlconn)
mySqlAdapter.Fill(mydataset, strTableName)
sqlconn.Close()
mySqlAdapter = Nothing
Catch ex As Exception
If sqlconn.State = ConnectionState.Open Then
sqlconn.Close()
End If
Throw ex
End Try
Return mydataset
End Function
#End Region
#Region "資料插入操作，引數為insert陳述句和表名"
Public Sub dataInsert(ByVal strSql As String, ByVal strTableName As String)
Dim mysqlcomm As SqlClient.SqlCommand
Try
sqlconn.Open()
mysqlcomm = New SqlClient.SqlCommand(strSql, sqlconn)
mysqlcomm.ExecuteNonQuery()
sqlconn.Close()
mysqlcomm = Nothing
Catch ex As Exception
If sqlconn.State = ConnectionState.Open Then
sqlconn.Close()
End If
Throw ex
End Try
End Sub
#End Region
#Region "修改資料模塊，引數為updata和表名"
Public Sub dataUpdate(ByVal strSql As String, ByVal strTableName As String)
Dim mysqlcomm As New SqlClient.SqlCommand
Try
sqlconn.Open()
mysqlcomm = New SqlClient.SqlCommand(strSql, sqlconn)
mysqlcomm.ExecuteNonQuery()
sqlconn.Close()
mysqlcomm = Nothing
Catch ex As Exception
If sqlconn.State = ConnectionState.Open Then
sqlconn.Close()
End If
Throw ex
End Try
End Sub
#End Region
#Region "洗掉資料操作,引數為delete和要洗掉的表名"
Public Sub dataDelete(ByVal strSql As String, ByVal strTableName As String)
Dim mysqlcomm As New SqlClient.SqlCommand
Try
sqlconn.Open()
mysqlcomm = New SqlClient.SqlCommand(strSql, sqlconn)
mysqlcomm.ExecuteNonQuery()
sqlconn.Close()
mysqlcomm = Nothing
Catch ex As Exception
If sqlconn.State = ConnectionState.Open Then
sqlconn.Close()
End If
Throw ex
End Try
End Sub
#End Region
#Region "控制元件系結方法,引數為SQL存盤程序和DataGridView控制元件"
Public Sub BDDataToDataGridView(ByVal PRO As String, ByVal DGV As DataGridView)
sqlconn.Open()
Dim sqlcmd As New System.Data.SqlClient.SqlCommand
sqlcmd.Connection = sqlconn
Dim da As New System.Data.SqlClient.SqlDataAdapter()
da.SelectCommand = sqlcmd
da.SelectCommand.CommandType = CommandType.StoredProcedure
da.SelectCommand.CommandText = "select * from '" + PRO.ToString().Trim() + "'" '通過SQL的存盤程序系結資料
Dim ds As New DataSet()
da.SelectCommand.Connection = sqlconn
da.Fill(ds)
DGV.DataSource = ds.Tables(0)
DGV.Refresh()
End Sub
#Region "控制元件系結方法,引數為SQL存盤程序和ComboBox控制元件"
Public Sub BDToComboBox(ByVal PRO As String, ByVal ComboBox As ComboBox)
sqlconn.Open()
Dim sqlcmd As New System.Data.SqlClient.SqlCommand
sqlcmd.Connection = sqlconn
Dim da As New System.Data.SqlClient.SqlDataAdapter()
da.SelectCommand = sqlcmd
da.SelectCommand.CommandText = "select * from '" + ComboBox.SelectedText.Trim + "'" '通過SQL的存盤程序系結資料
Dim ds As New DataSet()
da.SelectCommand.Connection = sqlconn
da.Fill(ds)
ComboBox.DataSource = ds.Tables(0)
ComboBox.Refresh()
End Sub
#End Region
#End Region
End Class
#End Region
uj5u.com熱心網友回復：
錯誤提示那么清晰明了：connectionstring沒有設定嘛然后看你的代碼，在open_conn方法里面進行了設定。那么接下來的問題就是這個方法被呼叫了嗎？最簡單的辦法，在這一行加個斷點，看在報錯前會不會跑到這個斷點就明白了。
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