VB鏈接SQL服務器的問題

Question

我收到一個錯誤如下：

從類型轉換「的SqlConnection爲鍵入「串」是無效的。

我的VB編碼是：

Dim conn As New SqlConnection 
    Dim cmd As New SqlCommand 
    Dim da As New SqlDataAdapter 
    Dim dt As New DataTable 
    Dim sSQL As String = String.Empty 
    Try 
     conn = New SqlConnection(Get_Constring) 
     conn.Open() 
     cmd.Connection = conn 
     cmd.CommandType = CommandType.Text 
     sSQL = "SELECT * FROM HostTable" 
     If Me.cboSearchBy.Text = "Name" Then 
      sSQL = sSQL & " where HOSTNAME like '%" & Me.txtSearch.Text & "%'" 
     ElseIf Me.cboSearchBy.Text = "Function" Then 
      sSQL = sSQL & " where FUCTION like '%" & Me.txtSearch.Text & "%'" 
     End If 
     cmd.CommandText = sSQL 
     da.SelectCommand = cmd 
     da.Fill(dt) 

     Me.dtgResult.DataSource = dt 
     If dt.Rows.Count = 0 Then 
      MsgBox("No record found!") 
     End If 
Function Get_Constring() 
    If Microsoft.VisualBasic.Right(Application.StartupPath, 1) = "\" Then 
     sConnstring = New SqlConnection("server=192.168.1.111\SQLSERVER;database=Common_DB;User ID=sa;Password=12345678") 
    Else 
     sConnstring = New SqlConnection("server=192.168.1.111\SQLSERVER;database=Common_DB;User ID=sa;Password=12345678") 
    End If 
    Return sConnstring 
End Function 

Answer 1

您在New SqlConnection中硬編碼的參數是實際的連接字符串。

您可能需要寫類似：

sConnstring = "server=192.168.1.111\SQLSERVER;database=Common_DB;User ID=sa;Password=12345678" 
myConnection = New SqlConnection(sConnstring) 

所以你的函數Get_Constring應該只返回字符串，而不是一個完整的連接。

Function Get_Constring() 
If Microsoft.VisualBasic.Right(Application.StartupPath, 1) = "\" Then 
    sConnstring = "server=192.168.1.111\SQLSERVER;database=Common_DB;User ID=sa;Password=12345678" 
Else 
    sConnstring = "server=192.168.1.111\SQLSERVER;database=Common_DB;User ID=sa;Password=12345678" 
End If 
Return sConnstring 

這應該按預期工作。

Answer 2

從類型 '的SqlConnection' 轉換到類型 '串' 是無效的。

此錯誤消息非常明確。您不能將（新）SqlConnection轉換爲字符串（sConnstring）。