如何在Vb 2010中使用SQL中的參數（Web開發人員）

Question

我正在努力解決SQL中的代碼VB但我遇到問題我有一個簡單的數據庫與表管理員UserName和Password列。

我希望能夠從文本框中讀取數據，然後將其輸入到一個SQL字符串中＆hellip; SQL字符串的工作原理（我測試了它），我可以用簡單的SELECT語句得到它，但我似乎無法讓SQL讀取我的參數。

幫助？

Protected Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
    Call Password_Check(txtTestInput.Text) 
End Sub 

Public Sub Password_Check(ByVal Answer As String) 

    Dim con As New SqlConnection 
    Dim cmd As New SqlCommand 
    Dim parameter As New SqlParameter("@Username", Answer) 
    Try 

     con.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("Database1ConnectionString1").ConnectionString 
     con.Open() 
     cmd.Connection = con 
     cmd.CommandText = " SELECT Password FROM Admin WHERE (UserName = @Username)" 
     cmd.Parameters.Add(parameter) 
     Dim lrd As SqlDataReader = cmd.ExecuteReader() 

     While lrd.Read() 
      Dim sothing As String 

      sothing = lrd("Password").ToString 
      If lrd("Password").ToString = txtPassword.Text Then 
       lblTestData.Text = "passwordSuccess" 
      ElseIf lrd("Password").ToString <> txtPassword.Text Then 
       lblTestData.Text = "passwordFail...:(" 
      End If 
     End While 

    Catch ex As Exception 
     lblTestData.Text = "Error while retrieving records on table..." & ex.Message 
    Finally 
     con.Close() 
    End Try 

End Sub 

Answer 1

在你的代碼上面

： - >Dim parameter As New SqlParameter("@Username", Answer)

我可以建議兩個選項：

Dim parameter As New SqlParameter("@Username", sqldbtype.nvarchar) 

parameter.value = Answer 

或

cmd.CommandText = string.format("SELECT Password FROM Admin WHERE (UserName = {0})", Answer) 

全碼：

Public Sub Password_Check(ByVal Answer As String) 

    Dim con As New SqlConnection 
    Dim cmd As New SqlCommand 
    Dim parameter As New SqlParameter("@Username", SqlDbType.NVarChar) 
    parameter.Value = Answer 
    Try 

     con.ConnectionString = System.Configuration.ConfigurationManager.ConnectionStrings("Database1ConnectionString1").ConnectionString 
     con.Open() 
     cmd.Connection = con 
     cmd.CommandText = "SELECT Password FROM Admin WHERE (UserName = @Username)" 
     cmd.Parameters.Add(parameter) 
     Dim lrd As SqlDataReader = cmd.ExecuteReader() 

     While lrd.Read() 
      Dim sothing As String 

      sothing = lrd("Password").ToString 
      If lrd("Password").ToString = txtPassword.Text Then 
       lblTestData.Text = "passwordSuccess" 
      ElseIf lrd("Password").ToString <> txtPassword.Text Then 
       lblTestData.Text = "passwordFail...:(" 
      End If 
     End While 

    Catch ex As Exception 
     lblTestData.Text = "Error while retrieving records on table..." & ex.Message 
    Finally 
     con.Close() 
    End Try 

End Sub 

Answer 2

關於您的數據庫系統有可能它不支持參數名稱。你有沒有嘗試過 ？您使用的Wat數據庫系統？

cmd.CommandText = " SELECT Password FROM Admin WHERE (UserName = ?)"