如何刷新c＃中的表单？

Question

I've built a form which can add/delete records to an SQL database. When I add a record, I want the form to reload and the listbox with all the records to now include the newly added record.

I googled this and saw that a new thread was recommended to refresh the form, but the instructions weren't clear enough for a newbie like me.

Any help would be appreciated.

Thanks in advance.

Edit: this is a desktop app using c# and not asp.

Some of the controls are populated by a wizard that I ran and for others I coded the datasource myself.

namespace LomWindows
{
    public partial class Form1 : Form
    {
        SqlConnection myConnection;

        public Form1()
        {
            InitializeComponent();
            myConnection = new SqlConnection(global::LomWindows.Properties.Settings.Default.esConnectionString);
            tConnStr.Text = global::LomWindows.Properties.Settings.Default.esConnectionString;

            try
            {
                myConnection.Open();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string sqlComm = "INSERT INTO ES_TOOL ....";

            try
            {
                myCommand.ExecuteNonQuery();
            }
            catch (Exception exce)
            {
                Console.WriteLine(exce.ToString());
            }

            try
            {
                myConnection.Close();
            }
            catch (Exception exc)
            {
                Console.WriteLine(exc.ToString());
            }

            InitializeComponent();
            MessageBox.Show("Tool Added");
            this.Invalidate();
        }
    }
}

Answer 1

您可以在添加/编辑/删除后再次重新绑定控件，这将使用更新的数据重新加载控件。

Answer 2

WinForms

There is a great article over at MSDN covering the following: Give Your .NET-based Application a Fast and Responsive UI with Multiple Threads .

When you want to Re-draw your window you can call the method Invalidate . However when you Re-bind a control; setting a new datasource, it will update the content in it.

Here are some great videos to watch for WinForms: "How Do I Videos" from WindowsClient.net .

WPF

Here is a matching article to the one in WinForms covering: Build More Responsive Apps With The Dispatcher .

Herer are some great videos to watch for WPF: "How Do I Videos" , aslo from WindowsClient.net.

ASP.NET

If you want to create more responsive webbapps you might want to consider having a look at jQuery and Ajax. You can then request a new part of your web-site and replace the old one.

However if you are just doing a postback and you want to add items to your listbox, you can just call DataBind on the ListBox and it should re-bind the items in the data-source.

Answer 3

The underlying question isn't really about Winforms repaints, rather it's how to freshen the datasource to which the Winform controls are bound, or from which the controls are being manually populated in unbound mode, after the database has been changed by your client application.

Unless you create the data model, your datasource object has no way of knowing that the data have been changed when a DML statement is executed by a command somewhere. It all has to be "tied together". ADO.NET uses a 'disconnected recordset' model. The ADO.NET datalayer objects will raise events related to data i/o and data errors, and you must must attach listeners/eventhandlers to them; these eventhandlers must, in turn, invoke your presentation-layer code.

At present you're just scratching the surface with the command object. Best thing to do would be to read one of the books that show you how to wire up eventhandlers to the ADO.NET event model.

EDIT: Here's a link to get you started: http://msdn.microsoft.com/en-us/library/w9y9a401.aspx

Answer 4

If it's ASP.NET you can refresh the form by redirecting it to itself by using the following code:

Response.Redirect(Request.RawRul);

If it's a Windows Application, you need to rebind the listbox control by setting its DataSource property again.

Answer 5

If you're already calling Invalidate on the ListBox, you might want to add a debug statement to the Paint method to make sure it's really repainting. If it is, then you should look into where Paint gets the state needed to draw the items. Do you query the database inside Paint ? (I hope not.) Or is the form keeping its state in memory somewhere? In that case, you should make sure that you're keeping the in-memory state consistent with the database.

Answer 6

Have you thought of the performance impact of re-loading all the rows whenever one row is added/deleted/updated? IMHO, reloading the entire data will just annoy the users and also increase the bandwidth usage. Instead, create POCO objects for each line of data. Whenever there is a (successful) CRUD operation (which you perform on the BackgroundWorker component), just add it to the DataSource and call DataBind .

For more information on how to use BackgroundWorker , see this .

Answer 7

Write Select query in Form_Load and call after where ever you need to refresh your form like,

form_load(Object sender,Event_args e)
  {

   select Query to display on Loading form
  }
add_click(Object sender,Event_args e)
 {
 form_load(sender,e);
 }