ado.net中使用vb.net的奇怪工作流程 [英] strange workflow in ado.net with vb.net

问题描述

Hello Professionals，

Hello Professionals,

i had assigned a assignment for insert,update, delete operation in a table for my student. he had done this assignment fine. but his code made me crazy that he wrote update code like below

Working sample:

Public Function Toeditdetails(ByVal item As Boolean)

        If item = True Then

            Dim con As SqlConnection
            Dim retval As Integer

            con = New SqlConnection(conn)
            con.Open()
            Dim cmd As SqlCommand
            cmd = New SqlCommand("updatelogin", con)
            cmd.CommandType = CommandType.StoredProcedure


            cmd.Parameters.Add(New SqlParameter("@username", SqlDbType.VarChar, 100)).Value() = TextBox1.Text.Trim()
            cmd.Parameters.Add(New SqlParameter("@user_password", SqlDbType.VarChar, 30)).Value() = TextBox2.Text.Trim()
            cmd.Parameters.Add(New SqlParameter("@nameofuser", SqlDbType.VarChar, 100)).Value() = TextBox3.Text.Trim()
            cmd.Parameters.Add(New SqlParameter("@contact_no", SqlDbType.VarChar, 10)).Value() = TextBox4.Text.Trim()
            cmd.Parameters.Add(New SqlParameter("@email", SqlDbType.VarChar, 100)).Value() = TextBox5.Text.Trim()
            cmd.Parameters.Add(New SqlParameter("@joiningdate", SqlDbType.Date)).Value() = DateTimePicker1.Value
            cmd.Parameters.Add(New SqlParameter("@usergroup_id", SqlDbType.Int)).Value() = SelectedID(ComboBox1.Text)

            If item = True Then
                cmd.Parameters.Add(New SqlParameter("@id", SqlDbType.Int)).Value() = Label9.Text.Trim()
            End If

            Dim da As SqlDataAdapter
            da = New SqlDataAdapter(cmd)
            Dim dst As New DataSet
            da.Fill(dst)

            If dst.Tables.Count > 0 Then
                DataGridView1.DataSource = dst.Tables(0)
            End If

            If Not cmd Is Nothing Then
                cmd.Dispose()
            End If
        End If

End Function

Note there is no ExecuteNonQuery() method for his SqlCommand object and he didn't call this method in entire project. when i call this function result still updating... how its happen? anyone genius can you explain what's going on above statement? any help would be appreciated

问候并感谢

Regards and Thanks

推荐答案

原因它发生的原因是你的学生正在使用仍然执行代码的数据集和SqlDataAdapter（da.Fill）。通常它们用于选择数据，您可以使用SqlCommand进行更新/插入，但这种方法仍然有效。

The reason it happens is because your student is using a DataSet and SqlDataAdapter which still executes code (da.Fill). Normally they are used for selecting data and you would use the SqlCommand for updating/inserting but this method can still work.

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