如何使用 c# asp.net 从具有逗号分隔值的列的表中获取记录？

Question

i was trying to get records from comma separated values from MySQL database by passing checkboxlist selected values in where clause using c# asp.net.

example:- i have table in following manner

ID | tshirt_img | Color

1 | ImgPath | Red,Green

2 | ImgPath | Orange,Yellow

           <asp:CheckBoxList runat="server"  ID="Chk_Colors" Font-Size="Small" 
           AutoPostBack="true" CssClass="chk1" 
           OnSelectedIndexChanged="Chk_Colors_SelectedIndexChanged" RepeatColumns="3" 
           RepeatDirection="Horizontal">
         <asp:ListItem> Red </asp:ListItem>
         <asp:ListItem> Green </asp:ListItem>
         <asp:ListItem> Orange </asp:ListItem>
         </asp:CheckBoxList>

       <asp:Repeater ID="rptr_data" runat="server">
        <ItemTemplate>
        <div class="display-image-box" >
         <img class="display-img" src='<%# Eval("tshirt_img") %>'>
       </div>
     <div class="display-image-box" >
     <h1><%# Eval("Color") %> </h1>
      </div>
    </ItemTemplate>
      <asp:Repeater>
 
 
    protected void Chk_Colors_SelectedIndexChanged(object sender, EventArgs e)
    {
        try
        {

            string selecteditems = String.Join(",",Chk_Colors.Items.OfType<ListItem>().Where(r 
            => r.Selected).Select(r => r.Text));
            string valueschk = selecteditems;
            string str = "select * from  tbl_colors where Color IN ('" +selecteditems+ "')";
            MySqlConnection con1 = new MySqlConnection(constr);
            MySqlCommand cmd1 = new MySqlCommand(str, con1);
            MySqlDataAdapter da1 = new MySqlDataAdapter();
            da1.SelectCommand = cmd1;
            DataTable dt1 = new DataTable();
            da1.Fill(dt1);
            rptr_data.DataSource = dt1;
            rptr_data.DataBind();

        }
        catch (Exception ex)
        {

        }
       }

Answer 1

The only correct answer to your problem is to fix the real problem of a bad database design. From experience we know that every hack you have to implement to cope with bad design will make the amount of code needed to solve a trivial problem grow exponentially. And one day it will be impossible to maintain and extend your code using a healthy or profitable balance of time an resources. Complexity will introduce more bugs than you can fix (as those fixes will likely introduce other bugs).

Your problem is that you are violating the data atomicity rule: each column must only contain a single value. Following this rule will always lead to simple code to handle queries and allows you to use strong column types (for example numeric instead of text columns). You would never have asked your question if you had followed this rule.

This kind of design optimization is very common and called "database normalization".
There are usually three normal forms that you should always try to implement. Actually, your problem is the very first normalization step or normal form, referred to as "1NF" (first normal form).
You should read What is Database Normalization? . It's a very brief article with a nice example. The example applies the normal forms step by step. I'm sure you can apply the example directly to your database without any effort (it's less effort than botching your database handling, for sure).

I guess that this is not the answer you want to hear, but this is the only answer any serious developer can give. Your current problem, and those many more to come following up, is solved by some very simple design changes. It's a problem that shouldn't be there in the first place ie it's not a normal problem. Don't already mess up the foundation.