Question

vb.net 连接SQL数据库登录代码

我的代码是连接到SQL数据库，输入用户密码，点登录，然后打开下一个界面，现在数据库是连上了，但IF语句无效，直接走ELSE，菜鸟一个，高手帮我改改～（这段代码原来连的是ACCESS数据源库） Dim sConnString As String = _ "Data Source =(local);Initial Catalog =LiMin SuperMarket Manage System;Integrated Security=SSPI" Dim myCn As New SqlConnection Private Sub OK_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles OK.Click Try myCn.ConnectionString = sConnString myCn.Open() Dim mySQL As String = "Select PersonnelID From Users Where Account='" & Me.boxname.Text & "' And Code='" & Me.PasswordTextBox.Text & "'" Dim sComm As New SqlCommand(mySQL, myCn) Dim s As Object = sComm.ExecuteScalar If sComm.ExecuteScalar Then Dim User_MainForm As New form1 User_MainForm.Show() Else MsgBox("用户名或密码不正确，请重试！") End If Catch ex As OleDbException MsgBox(ex.Message) Finally myCn.Close() '关闭连接 End Try End Sub

Answer 1

问题应该出在你的查询语句的结果没有值,你用你的查询语句到SQL中是否有返回值?记得加上你的条件,另外,你语句里这一句是多余的.Dim s As Object = sComm.ExecuteScalar 以下语句测试正常 Dim myCn As New SqlClient.SqlConnection Try myCn.ConnectionString = sConnString myCn.Open() Dim mySQL As String = "SELECT * FROM ygzl" Dim sComm As New SqlClient.SqlCommand(mySQL, myCn) If sComm.ExecuteScalar Then Dim User_MainForm As New Form1 User_MainForm.Show() Else MsgBox("用户名或密码不正确，请重试！") End If Catch ex As Exception MsgBox(ex.Message) Finally myCn.Close() '关闭连接 End Try