#using <mscorlib.dll>
#using <System.dll>
using namespace System;
using namespace System::Text;
using namespace System::IO;
using namespace System::Net;
using namespace System::Net::Sockets;
using namespace System::Collections;
错误：IntelliSense：“#using”需要启用 C++/CLI....
如何解决这个问题！？
【问题讨论】：
标签： c++-cli
您的项目设置有误。特别是配置属性、常规、公共语言运行时支持。
通过在 CLR 节点中选择一个项目模板来启动您的项目，从而进入成功的陷阱。
【讨论】：
从菜单栏中选择Project -> Properties。在Project properties 窗口中，在配置Properties -> General 下，确保将Common Language Runtime Support 设置为Common Language Runtime Support (/clr)
在 VS2019 中，步骤如下：
1/右键项目
2/Project
3/Properties
4/Configuration Properties
5/Advanced
6/Common Language Runtime Support改成Common Language Runtime Support(/clr)
【讨论】：
在您的项目设置中启用它（右键单击项目 -> 设置）第一个选项卡应提供该选项。
【讨论】：
MSDN 有一个很好的示例来测试性能差异，Parse 与 tryParse： Stopwatch Example
#include <stdio.h>
#using <System.dll>
using namespace System;
using namespace System::Diagnostics;
void DisplayTimerProperties()
{
// Display the timer frequency and resolution.
if (Stopwatch::IsHighResolution)
{
Console::WriteLine("Operations timed using the system's high-resolution performance counter.");
}
else
{
Console::WriteLine("Operations timed using the DateTime class.");
}
Int64 frequency = Stopwatch::Frequency;
Console::WriteLine(" Timer frequency in ticks per second = {0}", frequency);
Int64 nanosecPerTick = (1000L * 1000L * 1000L) / frequency;
Console::WriteLine(" Timer is accurate within {0} nanoseconds", nanosecPerTick);
}
void TimeOperations()
{
Int64 nanosecPerTick = (1000L * 1000L * 1000L) / Stopwatch::Frequency;
const long numIterations = 10000;
// Define the operation title names.
array<String^>^operationNames = { "Operation: Int32.Parse(\"0\")","Operation: Int32.TryParse(\"0\")","Operation: Int32.Parse(\"a\")","Operation: Int32.TryParse(\"a\")" };
// Time four different implementations for parsing
// an integer from a string.
for (int operation = 0; operation <= 3; operation++)
{
// Define variables for operation statistics.
Int64 numTicks = 0;
Int64 numRollovers = 0;
Int64 maxTicks = 0;
Int64 minTicks = Int64::MaxValue;
int indexFastest = -1;
int indexSlowest = -1;
Int64 milliSec = 0;
Stopwatch ^ time10kOperations = Stopwatch::StartNew();
// Run the current operation 10001 times.
// The first execution time will be tossed
// out, since it can skew the average time.
for (int i = 0; i <= numIterations; i++)
{
Int64 ticksThisTime = 0;
int inputNum;
Stopwatch ^ timePerParse;
switch (operation)
{
case 0:
// Parse a valid integer using
// a try-catch statement.
// Start a new stopwatch timer.
timePerParse = Stopwatch::StartNew();
try
{
inputNum = Int32::Parse("0");
}
catch (FormatException^)
{
inputNum = 0;
}
// Stop the timer, and save the
// elapsed ticks for the operation.
timePerParse->Stop();
ticksThisTime = timePerParse->ElapsedTicks;
break;
case 1:
// Parse a valid integer using
// the TryParse statement.
// Start a new stopwatch timer.
timePerParse = Stopwatch::StartNew();
if (!Int32::TryParse("0", inputNum))
{
inputNum = 0;
}
// Stop the timer, and save the
// elapsed ticks for the operation.
timePerParse->Stop();
ticksThisTime = timePerParse->ElapsedTicks;
break;
case 2:
// Parse an invalid value using
// a try-catch statement.
// Start a new stopwatch timer.
timePerParse = Stopwatch::StartNew();
try
{
inputNum = Int32::Parse("a");
}
catch (FormatException^)
{
inputNum = 0;
}
// Stop the timer, and save the
// elapsed ticks for the operation.
timePerParse->Stop();
ticksThisTime = timePerParse->ElapsedTicks;
break;
case 3:
// Parse an invalid value using
// the TryParse statement.
// Start a new stopwatch timer.
timePerParse = Stopwatch::StartNew();
if (!Int32::TryParse("a", inputNum))
{
inputNum = 0;
}
// Stop the timer, and save the
// elapsed ticks for the operation.
timePerParse->Stop();
ticksThisTime = timePerParse->ElapsedTicks;
break;
default:
break;
}
// Skip over the time for the first operation,
// just in case it caused a one-time
// performance hit.
if (i == 0)
{
time10kOperations->Reset();
time10kOperations->Start();
}
else
{
// Update operation statistics
// for iterations 1-10001.
if (maxTicks < ticksThisTime)
{
indexSlowest = i;
maxTicks = ticksThisTime;
}
if (minTicks > ticksThisTime)
{
indexFastest = i;
minTicks = ticksThisTime;
}
numTicks += ticksThisTime;
if (numTicks < ticksThisTime)
{
// Keep track of rollovers.
numRollovers++;
}
}
}
// Display the statistics for 10000 iterations.
time10kOperations->Stop();
milliSec = time10kOperations->ElapsedMilliseconds;
Console::WriteLine();
Console::WriteLine("{0} Summary:", operationNames[operation]);
Console::WriteLine(" Slowest time: #{0}/{1} = {2} ticks", indexSlowest, numIterations, maxTicks);
Console::WriteLine(" Fastest time: #{0}/{1} = {2} ticks", indexFastest, numIterations, minTicks);
Console::WriteLine(" Average time: {0} ticks = {1} nanoseconds", numTicks / numIterations, (numTicks * nanosecPerTick) / numIterations);
Console::WriteLine(" Total time looping through {0} operations: {1} milliseconds", numIterations, milliSec);
}
}
int main()
{
DisplayTimerProperties();
Console::WriteLine();
Console::WriteLine("Press the Enter key to begin:");
Console::ReadLine();
Console::WriteLine();
TimeOperations();
getchar();
}
//Operations timed using the system's high-resolution performance counter.
//Timer frequency in ticks per second = 3319338
//Timer is accurate within 301 nanoseconds
//
//Press the Enter key to begin :
//
//
//
//Operation : Int32.Parse("0") Summary :
// Slowest time : #4483 / 10000 = 95 ticks
// Fastest time : #3 / 10000 = 0 ticks
// Average time : 0 ticks = 99 nanoseconds
// Total time looping through 10000 operations : 1 milliseconds
//
// Operation : Int32.TryParse("0") Summary :
// Slowest time : #7720 / 10000 = 187 ticks
// Fastest time : #1 / 10000 = 0 ticks
// Average time : 0 ticks = 109 nanoseconds
// Total time looping through 10000 operations : 1 milliseconds
//
// Operation : Int32.Parse("a") Summary :
// Slowest time : #3701 / 10000 = 2388 ticks
// Fastest time : #2698 / 10000 = 102 ticks
// Average time : 116 ticks = 35109 nanoseconds
// Total time looping through 10000 operations : 352 milliseconds
//
// Operation : Int32.TryParse("a") Summary :
// Slowest time : #8593 / 10000 = 23 ticks
// Fastest time : #1 / 10000 = 0 ticks
// Average time : 0 ticks = 88 nanoseconds
// Total time looping through 10000 operations : 1 milliseconds
【讨论】：
如果您使用的是 Visual Studio，您可能需要预先进行一些安装。要安装它们，请从 Windows 开始菜单中打开 Visual Studio 安装程序。确保选中 Desktop development with C++ 磁贴，并在 Optional components 部分中选中 C++/CLI Support。
【讨论】：