小编Com*_*ewb的帖子

每次我尝试连接到数据库时,它都会给我这个错误"ConnectionString属性尚未初始化"

我该怎么做才能解决这个问题？

这是我的代码

Module Module1
    Function GetInfoForStudent(ByRef QueryName As String, ByVal UserName As String, ByVal Password As String) As DataTable
        Using Con As New SqlConnection
            Try
                Using OleCon As New SqlConnection
                    Dim Connection As String = "Data Source=.\SQLEXPRESS;AttachDbFilename=G:\VB Project\Library
Catalog System\Library Catalog System\library.mdf;Integrated
Security=True;Connect Timeout=30;User Instance=True"
                    Con.Open()
                    Dim Cmd As SqlCommand = Con.CreateCommand()
                    Cmd.CommandType = CommandType.StoredProcedure
                    Cmd.CommandText = QueryName
                    Cmd.Parameters.AddWithValue("@user", UserName)
                    Cmd.Parameters.AddWithValue("@pass", Password)
                    Dim da As New SqlDataAdapter(Cmd)
                    Dim ds As New DataTable()
                    da.Fill(ds)
                    Return ds
                End Using
            Catch ex …

我有3张桌子

   Student    Loan    Book
 - StudentID  LoanID  BookID

我需要设置哪些外键,因此在给出学生姓名时,搜索该学生的所有贷款并显示书籍详细信息