Question

数据库位于sqlYog，

当我运行此程序时，我收到错误：
CommandText属性尚未正确初始化。？

请帮帮我

Imports MySql.Data.MySqlClient
Imports System.Data

Partial Class login
    Inherits System.Web.UI.Page

Public dbconn As New MySqlConnection
Public sql As String
Public dbcomm As New MySqlCommand
Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

    dbconn = New MySqlConnection("data source= localhost; user id=root; password=search; database=bookstore;")
    dbconn.Open()
    dbcomm.Connection = dbconn

End Sub

Protected Sub btn_login_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btn_login.Click

    Try
        dbcomm = New MySqlCommand(sql, dbconn)

        sql = "select * from bookstore.lib_user where username=@username  and password=@password"

        dbcomm.Parameters.AddWithValue("@username", txt_username.Text)
        dbcomm.Parameters.AddWithValue("@password", txt_password.Text)

        Dim dbadpt As New MySqlDataAdapter(dbcomm)
        Dim dt As New DataTable()
        dbadpt.Fill(dt)
        If dt.Rows.Count > 0 Then
            MsgBox("login is suceesfull")
        Else
            Literal1.Text = "invalid login"
        End If

        Catch ex As Exception
            MsgBox("read this error: " + ex.Message)
        End Try
    End Sub
End Class

Answer 1

请更改行的顺序。

首先设置查询文本，然后调用命令构造函数。

sql = "select * from bookstore.lib_user where username=@username  and password=@password"
dbcomm = New MySqlCommand(sql, dbconn)

Answer 2

根据您的代码sql在分配到MySqlCommand时为空时，您需要先设置sql值，然后将其分配给MySqlCommand对象。

sql = "select * from bookstore.lib_user where username=@username  and password=@password"

 dbcomm = New MySqlCommand(sql, dbconn)

如何避免错误：“CommandText属性尚未正确初始化”？

2 个答案: