如何在代码中实现ienumerable？ [英] How to implement ienumerable in code?

问题描述

嗨！我想在我的代码中实现不可数，以便它只读，但我不知道在哪里实现它。到目前为止，我还没有找到任何可能解决我问题的互联网解决方案。截至目前，我只使用List并希望在我的代码中集成ienumerable。此外，如果您发现编码错误，请随时提出建议。



我尝试过：

Hi! i wanted to implement ienumerable in my code so that it is readonly but i don't know where to possibly implement it. So far i haven't found any solution in the internet that might answer my problem. As of now, i have only used List and wanted to integrate ienumerable in my code. Also, feel free to suggest anything if you notice bad coding practices.

What I have tried:

public static List<GuitarItems> GetGuitarItems(string itemCategory)
    {
        List<GuitarItems> list = new List<GuitarItems>();
        string query = string.Format("SELECT * FROM guitarItems WHERE brand LIKE @brand");

        try
        {
            conn1.Open();
            command1.CommandText = query;
            command1.Parameters.Add(new SqlParameter("brand", itemCategory));
            SqlDataReader reader = command1.ExecuteReader();

            while (reader.Read())
            {
                int id = reader.GetInt32(0);
                string type = reader.GetString(1);
                string brand = reader.GetString(2);
                string model = reader.GetString(3);
                double price = reader.GetDouble(4);
                string itemimage1 = reader.GetString(5);
                string itemimage2 = reader.GetString(6);
                string description = reader.GetString(7);
                string necktype = reader.GetString(8);
                string body = reader.GetString(9);
                string fretboard = reader.GetString(10);
                string fret = reader.GetString(11);
                string bridge = reader.GetString(12);
                string neckpickup = reader.GetString(13);
                string bridgepickup = reader.GetString(14);
                string hardwarecolor = reader.GetString(15);

                GuitarItems gItems = new GuitarItems(id, type, brand, model, price, itemimage1, itemimage2, description, necktype, body,
                    fretboard, fret, bridge, neckpickup, bridgepickup, hardwarecolor);
                list.Add(gItems);
            }
        }
        finally
        {
            conn1.Close();
            command1.Parameters.Clear();
        }

        return list;
    }

以下是其他代码：

And here is the other code:

private void FillPage()
    {
        List<GuitarItems> itemList = new List<GuitarItems>();
        List<string> itemListPage = new List<string>();

        itemList = ConnectionClassGuitarItems.GetGuitarItems(brandType);
       
        StringBuilder sb = new StringBuilder();

        foreach (GuitarItems gList in itemList)
        {
            itemListPage.Add("GuitarItemsIbanezDetails" + (x + 1) + ".aspx");
           
            sb.Append(
                    string.Format(
                        @"
                        <div class='one-two'>
                            <a href='{3}' runat='server'><img runat='server' src='{0}'/></a>
                            <div class='content'>
                                <div id='label'>{1} {2}</div>
                            </div>
                        
                    </div>", gList.ItemImage1, gList.Brand, gList.Model, itemListPage[x]));

            x++;
            
        }
  

        lblOutput.Text = sb.ToString();

    }

推荐答案

使用迭代器方法：

Use an iterator method:

public static IEnumerable<GuitarItems> GetGuitarItems(string itemCategory)
{
    using (var con = new SqlConnection("..."))
    using (var cmd = new SqlCommand("SELECT * FROM guitarItems WHERE brand LIKE @brand", con))
    {
        cmd.Parameters.AddWithValue("@brand", itemCategory);
        
        con.Open();
        using (var reader = cmd.ExecuteReader(CommandBehavior.CloseConnection))
        {
            while (reader.Read())
            {
                int id = reader.GetInt32(0);
                ...
                
                yield return new GuitarItems(id, ...);
            }
        }
    }
}

或使用 Dapper [ ^ ]，正如我建议的那样在您的最新问题 [ ^ ]。

Or use Dapper[^], as I suggested in your latest question[^].

public static IEnumerable<GuitarItems> GetGuitarItems(string itemCategory)
{
    using (var con = new SqlConnection("..."))
    {
        return con.Query<GuitarItems>("SELECT * FROM guitarItems WHERE brand LIKE @brand", new { brand = itemCategory });
    }
}

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