DropDownList dynamic generation method in C

2021-01-19 22:21:18
OfStack

This article illustrates the dynamic DropDownList generation method in C#. Share with you for your reference. The specific analysis is as follows:

Today, I learned DropDownList dynamic generation and asp.net life cycle, and ViewState, because the project needs to dynamically generate conditions according to the requirements, so I studied a part of the code to complete these work, well, without more words, let's look at the code

First is the code of the web page:


<span style="font-size:18px;"><body>
  <form id="form1" runat="server">
  <div>
    <asp:PlaceHolder ID="PlaceHolder1" runat="server"></asp:PlaceHolder>
 //placeholder Control is equivalent to 1 A container for storing other controls 
    <br />
    <asp:Button ID="Button1" runat="server" OnClick="Button1_Click" Text="Button"/></div>
  </form>
</body></span>

Here is the c# program


public partial class _Default : System.Web.UI.Page
{
  private CategoryBLL _categoryBLL = new CategoryBLL();
  private Category _category = new Category();
  private void Page_Init(object sender, System.EventArgs e)
  // We can see 1 Under the asp The life cycle of 
  {
    BindDrpClass();
  }
  protected void Page_Load(object sender, EventArgs e)
  {
    string str = "8/14/19/25";
 // Database read 
    string[] arr = str.Split('/');
    if (arr.Length == PlaceHolder1.Controls.Count)
 // Prevent read errors when adding categories 
    {
      for (int i = 0; i < PlaceHolder1.Controls.Count; i++)
      {
        if (PlaceHolder1.Controls[i] is DropDownList)
        {
          ((DropDownList)PlaceHolder1.Controls[i]).SelectedValue = arr[i];
        }
      }
    }
  }
  private void BindDrpClass()
  {
    DataTable dt = _categoryBLL.GetCategory();
    DataRow[] drs = dt.Select("pid=0");
    foreach (DataRow dr in drs)
    {
      string id = dr["id"].ToString();
      string name = dr["name"].ToString();
      DropDownList ddl = new DropDownList();
      // Specific operations to add 
      ddl.Items.Clear();
      ddl.ID = "ddl" + id;
      ddl.Items.Add(new ListItem(" - " + name + " - ", id));
      PlaceHolder1.Controls.Add(ddl);
      int sonparentid = int.Parse(id);
      BindDrpNode(sonparentid, dt, ddl);
    }
  }
  private void BindDrpNode(int parentid, DataTable dt, DropDownList ddl)
  {
    DataRow[] drs = dt.Select("pid= " + parentid);
    foreach (DataRow dr in drs)
    {
      string id = dr["id"].ToString();
      string name = dr["name"].ToString();
      ddl.Items.Add(new ListItem(name, id));
      PlaceHolder1.Controls.Add(ddl);
    }
  }
  protected void Button1_Click(object sender, EventArgs e)
  {
    string category = "";
    string category2 = "";
    foreach (Control childControl in PlaceHolder1.Controls)
    {
      if (childControl is DropDownList) 
      {
        category += "/" + ((DropDownList)childControl).SelectedItem.Text;
        category2 += "/" + ((DropDownList)childControl).SelectedValue;
      }
    }
    if (category.Length > 0)
      category = category.Remove(0, 1);
    Response.Write(category);
    Response.Write("<br />"); 
    if (category2.Length > 0)
      category2 = category2.Remove(0, 1);
    Response.Write(category2);
  }
}

I hope this article is helpful to your C# program design.