asp.net中的treeview控件加载节点非常慢

Question

On my asp.net webpage, the treeview control has thousands of nodes and the tree is very slow to load. The nodes data is coming from sql database using the code below. What can we do to optimize or improve the performance.

public partial class TaxonomyAllTermsTree : System.Web.UI.Page
  {
  protected void Page_Load(object sender, EventArgs e)
  {

    if (!this.IsPostBack)
    {
        this.AddNodes(this.TreeView1.Nodes, 0, this.LoadData());
        TreeView1.CollapseAll();
    }

  }


  private void AddNodes(TreeNodeCollection nodes, int level, System.Data.DataTable dt)
  {
    string filterExp = string.Format("ParentID='{0}'", level);
    foreach (System.Data.DataRow r in dt.Select(filterExp))
    {
        TreeNode item = new TreeNode()
        {
            Text = r[2].ToString(),
            Value = r[1].ToString(),
            NavigateUrl = "SomeURL.aspx?TermID=" + r[0].ToString()
        };
        this.AddNodes(item.ChildNodes, int.Parse(r[0].ToString()), dt);
        nodes.Add(item);
    }
  }

  private System.Data.DataTable LoadData()
  {
    DataTable dt = new DataTable();
    string connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["ThesaurusConnectionString"].ConnectionString;

    using (SqlConnection connection = new SqlConnection(connectionString))
    {
        connection.Open();
        SqlCommand cmd = new SqlCommand("GetFullTree", connection);
        cmd.CommandType = CommandType.StoredProcedure;

        SqlDataAdapter da = new SqlDataAdapter(cmd);

        da.Fill(dt);

        return dt;
    }
  }
}

Answer 1

1) As mentioned by @Azhar set ExpandDepth to 0

ExpandDepth - gets or sets the number of levels that are expanded when a TreeView control is displayed for the first time.

2) Use ASP.NET caching to store the DataTable in cache for a certain period of time to avoid unnecessary database trips, which will most definitely improve performance.

Here are some helpful articles about caching:

1. How to Add items to the Cache
2. How to Delete items from the Cache

And here's an example

//The item will be in the cache for 10 minutes
DataTable table = LoadData();
Cache.Insert("TreeView", table, null, DateTime.Now.AddMinutes(10), TimeSpan.Zero);

Check if the key exists in Cache, if it does load the data from the cache, otherwise load the data from a db and insert it into the Cache:

if (Cache["TreeView"] != null)
{
    var table = Cache["TreeView"] as DataTable;
    //Do something with the DataTable
}
else
{
    DataTable table = LoadData();
    Cache.Insert("TreeView", table, null, DateTime.Now.AddMinutes(1), TimeSpan.Zero);
} 

Hope these example help you!