C# Signature:
[DllImport("kernel32.dll")]
static extern bool QueryPerformanceCounter(out long lpPerformanceCount);
VB.NET Signature:
<DllImport("kernel32.dll", SetLastError:=True)> _
Shared Function QueryPerformanceCounter(ByRef lpPerformanceCount As Long) As Boolean
End Function
User-Defined Types:
None.
Notes:
None.
Tips & Tricks:
For this particular method, execution time is often critical. Security can be traded for additional speed by applying the SuppressUnmanagedCodeSecurity attribute to the method declaration. This will prevent the runtime from doing a security stack walk at runtime.
[DllImport("kernel32.dll"),SuppressUnmanagedCodeSecurity]
static extern bool QueryPerformanceCounter(out long lpPerformanceCount);
Sample Code:
Imports System.Runtime.InteropServices
Imports System.Security
Friend Enum TimeState
Started
Stopped
End Enum
Public Class HighResTimer
<DllImport("kernel32.dll"), SuppressUnmanagedCodeSecurity()> _
Private Shared Function QueryPerformanceCounter(ByRef lpPerformanceCount As Long) As Boolean
End Function
<DllImport("kernel32.dll"), SuppressUnmanagedCodeSecurity()> _
Private Shared Function QueryPerformanceFrequency(ByRef lpPerformanceFreq As Long) As Boolean
End Function
Private Shared freq As Long
Shared Sub New()
If Not QueryPerformanceFrequency(freq) Then
Throw New System.ComponentModel.Win32Exception
End If
End Sub
Private startTime, endTime As Long
Private _duration As Double
Private state As TimeState = TimeState.Stopped
Public Sub Start()
If state = TimeState.Started Then
Throw New ApplicationException("Cant' start, already started")
End If
state = TimeState.Started
QueryPerformanceCounter(startTime)
End Sub
Public Function [Stop]() As Double
QueryPerformanceCounter(endTime)
If state = TimeState.Stopped Then
Throw New ApplicationException("Cant' start, already started")
End If
state = TimeState.Stopped
_duration = ((endTime - startTime) / freq)
Return _duration
End Function
Public ReadOnly Property Duration() As Double
Get
If state = TimeState.Started Then
Throw New ApplicationException("Must call Stop() first")
End If
Return _duration
End Get
End Property
End Class
Alternative Managed API:
