我该如何修复tbese错误？ [英] How do I fixed tbese error?

问题描述

错误：

Error:

"There is already an open DataReader associated with this Command which must be closed first"

如果数据库中已存在菜单名称，则显示错误信息，否则插入菜单名称。



我尝试了什么：

If the menu name is already exists in the database, display an error message else insert menu name.

What I have tried:

Public Sub addMenu()
        Try
            dbConnection()
            search_query = "SELECT * FROM tblfood_menu WHERE menu_name = @menu_name;"
            command = New SqlCommand
            With command
                .Connection = connection
                .CommandText = search_query
                .Parameters.Clear()
                .Parameters.Add(New SqlParameter With {.ParameterName = "@menu_name", .SqlDbType = SqlDbType.VarChar, .Value = formFoodMenu.txtMenuName.Text})
                dataReader = command.ExecuteReader()
                If dataReader.HasRows Then
                    MsgBox("Menu name is already exists!", MsgBoxStyle.Exclamation, "Add Menu")
                Else
                    insert_query = "INSERT INTO tblfood_menu(menu_name) VALUES(@menu_name);"
                    command = New SqlCommand
                    With command
                        .Connection = connection
                        .CommandText = insert_query
                        result = .ExecuteNonQuery()
                        If result = 0 Then
                            MsgBox("Error in adding menu!", MsgBoxStyle.Exclamation)
                        Else
                            MsgBox("Successfully added menu!", MsgBoxStyle.Information)
                        End If
                    End With
                End If
            End With
        Catch ex As SqlException
            MsgBox("Error: " + ex.Message)
        Finally
            connection.Close()
            command.Dispose()
        End Try
    End Sub

推荐答案

With command
                .Connection = connection
                .CommandText = search_query
                .Parameters.Clear()
                .Parameters.Add(New SqlParameter With {.ParameterName = "@menu_name", .SqlDbType = SqlDbType.VarChar, .Value = formFoodMenu.txtMenuName.Text})
                result = .ExecuteScalar()
                If result > 0 Then
                    MsgBox("Menu name is already exists!", MsgBoxStyle.Exclamation, "Add Menu")
                Else
                    insert_query = "INSERT INTO tblfood_menu(menu_name) VALUES(@menu_name);"
                    command = New SqlCommand
                    With command
                        .Connection = connection
                        .CommandText = insert_query
                        .Parameters.Clear()
                        .Parameters.Add(New SqlParameter With {.ParameterName = "@menu_name", .SqlDbType = SqlDbType.VarChar, .Value = formFoodMenu.txtMenuName.Text})
                        result = .ExecuteNonQuery()
                        If result = 0 Then
                            MsgBox("Error in adding menu!", MsgBoxStyle.Exclamation)
                        Else
                            MsgBox("Successfully added menu!", MsgBoxStyle.Information)
                        End If
                    End With
                End If
            End With

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