c# - what is the best way of providing instant search functionality as a user types in a textbox -

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i want user search employee name or employee number. have provided textbox. user types in textbox, handle _textchanged event , update datagridview list of employees employee name or employee number contains text user entering in textbox.

the problem having slows typing , the datagridview update because every time text changes in textbox, search query hits database. makes form how un responsive.

does 1 know of better approach?

  • simple: delay querying db half second or second ensure user has stopped typing remembering last time text has changed.
  • better in long term: if db query takes long time (more second) can outsource querying db thread (task or backgroundworker). can fill datagrid in own task if it's data drawing takes long. able implement canceling mechanism , have main gui elements remain responsive.

i thought in democode below:

using system; using system.collections.generic; using system.threading; using system.threading.tasks; using system.windows.forms;  namespace windowsformsapplication19 {     public partial class form1 : form     {         cancellationtokensource tokensource = new cancellationtokensource();          public form1()         {             initializecomponent();         }          private void textbox1_textchanged(object sender, eventargs e)         {             // cancel old query , datagrid update             tokensource.cancel();              tokensource = new cancellationtokensource();             var token = tokensource.token;              task.factory.startnew((s) =>                 {                     var q = task.factory.startnew<ienumerable<demodata>>(() => longlastingdataquery(textbox1.text, token), token);                     if (!token.iscancellationrequested)                         task.factory.startnew(() => binddata(q.result));                 }, token);         }          private ienumerable<demodata> longlastingdataquery(string search, cancellationtoken token)         {             list<demodata> l = new list<demodata>();             (int = 0; < 10000 * search.length; i++)             {                 if (token.iscancellationrequested)                     return l;                  l.add(new demodata { id = i, text = search + i, text1 = search + + i, text2 = search + + + i, text3 = search + + + + });             }             thread.sleep(1000);             return l;         }          private void binddata(ienumerable<demodata> enumerable)         {             if (datagridview1.invokerequired)                 datagridview1.invoke(new methodinvoker(() => binddata(enumerable)));             else             {                 demodatabindingsource.datasource = null;                 demodatabindingsource.datasource = enumerable;             }         }          public class demodata         {             public string text { get; set; }             public string text1 { get; set; }             public string text2 { get; set; }             public string text3 { get; set; }             public int id { get; set; }         }     } }

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