How to: Create a Custom TraceListener

The Telerik Data Access API provides the TraceAdapter class from the Telerik.OpenAccess.Diagnostic namespace. This class can be used to trace events dynamically and process them in the code. To use the class, another class deriving from TraceListener is required. The following code-snippet shows you the custom OpenAccessTraceListener class. It derives from the abstract System.Diagnostic.TraceListener and overrides some of its methods. In this example, the tracer class writes output messages to a TextBox control and counts the executed SQL Statements. Of course, you can implement your own custom logic to integrate the tracer into your application. The most important step here is to add the tracer to the Listeners collection of the singleton Telerik.OpenAccess.Diagnostics.TraceAdapter instance. This can be done in the constructor of the class. The WriteLine method filters the messages and prints only the SQL statements. They can be easily recognized because they start with the "driver.stat.exec" string. To use the custom traces class, just create an instance and initialize it.

C#


    using System;
    using System.Diagnostics;
    using System.Threading;
    using System.Windows.Forms;

    namespace CustomTraceListener
    {
       public class OpenAccessTraceListener : TraceListener
       {
           private int id;
           private int count;
           private TextBox textBox;
           private Thread myThread;

           public OpenAccessTraceListener(TextBox textBox) :
               base("Telerik Data Access")
           {
               this.myThread = Thread.CurrentThread;
               this.textBox = textBox;
               this.count = 0;

               Telerik.OpenAccess.Diagnostics.TraceAdapter.Instance.Level = "4";
               this.id = Telerik.OpenAccess.Diagnostics.TraceAdapter.Instance.Listeners.Add(this);
           }

           public override void Write(string message)
           {
               this.WriteLine(message);
           }

           public override void WriteLine(string message)
           {
               if (Object.ReferenceEquals(this.myThread, Thread.CurrentThread) == false)
                   return;

               if (message.StartsWith("driver.stat.exec"))
               {
                   count++;
                   int index;
                   if (message.IndexOf("SELECT") >= 0)
                       index = message.IndexOf("SELECT");
                   else
                       index = message.IndexOf("INSERT");

                   this.textBox.Text += String.Format("{0}: {1}\r\n", count.ToString(), message.ToString().Substring(index));
                   this.textBox.SelectionStart = this.textBox.Text.Length;
                   this.textBox.SelectionLength = 0;
                   this.textBox.ScrollToCaret();
               }
           }

           internal void Reset()
           {
               this.textBox.Text = String.Empty;
               this.count = 0;
           }

           protected override void Dispose(bool disposing)
           {
               this.textBox.Text += this.count.ToString() + " quires executed";
               base.Dispose(disposing);
           }
       }
    }

VB.NET


    Imports System.Threading

    Public Class OpenAccessTraceListener
        Inherits TraceListener
        Private id As Integer
        Private count As Integer
        Private _textBox As TextBox
        Private myThread As Thread

        Public Sub New(ByVal _textBox As TextBox)
            MyBase.New("Telerik Data Access")
            Me.myThread = Thread.CurrentThread
            Me._textBox = _textBox
            Me.count = 0
            Telerik.OpenAccess.Diagnostics.TraceAdapter.Instance.Level = "4"
            Me.id = Telerik.OpenAccess.Diagnostics.TraceAdapter.Instance.Listeners.Add(Me)
        End Sub

        Public Overloads Overrides Sub Write(ByVal message As String)
            Me.WriteLine(message)
        End Sub

        Public Overloads Overrides Sub WriteLine(ByVal message As String)
            If Object.ReferenceEquals(Me.myThread, Thread.CurrentThread) = False Then
                Return
            End If

            If message.StartsWith("driver.stat.exec") Then
                count += 1
                Dim index As Integer
                If message.IndexOf("SELECT") >= 0 Then
                    index = message.IndexOf("SELECT")
                Else
                    index = message.IndexOf("INSERT")
                End If

                Me._textBox.Text += String.Format("{0}: {1}" & vbCrLf, count.ToString(), message.ToString().Substring(index))
                Me._textBox.SelectionStart = Me._textBox.Text.Length
                Me._textBox.SelectionLength = 0
                Me._textBox.ScrollToCaret()
            End If
        End Sub

        Friend Sub Reset()
            Me._textBox.Text = String.Empty
            Me.count = 0
        End Sub

        Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
            Me._textBox.Text += Me.count.ToString() & " quires executed"
            MyBase.Dispose(disposing)
        End Sub
    End Class

See Also