Question

我收到如下错误：

从类型＆＃39; SqlConnection＆＃39;转换输入＆＃39; String＆＃39;无效。

我的VB编码是：

    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内硬编码的参数是实际的连接字符串。

你可能想要写一些类似的东西：

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

所以你的函数Get_Constring应该只返回字符串，而不是整个连接。

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

这应该按预期工作。

Answer 2

从“SqlConnection”类型到“String”类型的转换无效。

此错误消息非常清楚。您不能将（新）SqlConnection转换为字符串（sConnstring）。

VB链接SQL服务器问题

2 个答案: