如何用SQL SERVER内置的函数把NULL转换成空字符串
isnull(字段名,'')
如果字段为null,会得到空字符串;如果字段不为null,则会得到字段值
如何用SQL SERVER内置的函数把NULL转换成空字符串
isnull(字段名,'')
如果字段为null,会得到空字符串;如果字段不为null,则会得到字段值
ASP.NET MVC在Controller中,把JsonResult转为JSON字符串
string json = new System.Web.Script.Serialization.JavaScriptSerializer().Serialize(jsonResult.Data);
Response.Write(json);
使用System.IO.File.Create(path);创建的文件如何关闭
FileStream fs = System.IO.File.Create(path);
fs.Close();
使用下面的命令查看Hello.exe
所依赖的DLL:
windeployqt Hello.exe
如果还有缺少的DLL,可以根据报错提示用 Everything 工具进行查找,然后放进程序目录就行了。
qt quick 的程序要这样发布
-qmldir 后面是qt的qml目录
windeployqt daolan.exe -qmldir "D:\Qt\Qt5.8.0\5.8\mingw53_32\qml"
一个 VC++ 中使用的 HttpClient 类,可以进行HTTP GET和POST,代码如下:
HttpClient.h
#pragma once
#include <string>
#include <vector>
using namespace std;
class CHttpClient
{
public:
CHttpClient(void);
~CHttpClient(void);
BOOL Get(LPCSTR url, string &result);
};
HttpClient.cpp
#include "stdafx.h"
#include "HttpClient.h"
#include <wininet.h>
#pragma comment(lib, "wininet.lib")
CHttpClient::CHttpClient(void)
{
}
CHttpClient::~CHttpClient(void)
{
}
BOOL CHttpClient::Get(LPCSTR url, string &result)
{
result.clear();
vector<char> v;
const CHAR * szUrl = url;
CHAR szAgent[] = "";
HINTERNET hInternet1 =
InternetOpen(NULL,INTERNET_OPEN_TYPE_PRECONFIG,NULL,NULL,NULL);
if (NULL == hInternet1)
{
InternetCloseHandle(hInternet1);
return FALSE;
}
HINTERNET hInternet2 =
InternetOpenUrl(hInternet1,szUrl,NULL,NULL,INTERNET_FLAG_NO_CACHE_WRITE,NULL);
if (NULL == hInternet2)
{
InternetCloseHandle(hInternet2);
InternetCloseHandle(hInternet1);
return FALSE;
}
DWORD dwMaxDataLength = 500;
PBYTE pBuf = (PBYTE)malloc(dwMaxDataLength*sizeof(TCHAR));
if (NULL == pBuf)
{
InternetCloseHandle(hInternet2);
InternetCloseHandle(hInternet1);
return FALSE;
}
DWORD dwReadDataLength = NULL;
BOOL bRet = TRUE;
do
{
ZeroMemory(pBuf,dwMaxDataLength*sizeof(TCHAR));
bRet = InternetReadFile(hInternet2,pBuf,dwMaxDataLength,&dwReadDataLength);
for (DWORD dw = 0;dw < dwReadDataLength;dw++)
{
v.push_back(pBuf[dw]);
}
} while (NULL != dwReadDataLength);
vector<char>::iterator i;
for(i=v.begin(); i!=v.end(); i++)
result += *i;
return TRUE;
}
ProcessStartInfo 一定要写全路径,不然会出现一些莫明其妙的错误,比如开机自动启动时打不开。
ProcessStartInfo p1 = new ProcessStartInfo($"{Application.StartupPath}\\PD101AHelper.exe", $"{address} \"{windowShowMsg.Trim()}\" \"{zhShowMsg2 ?? ""}\"");
p1.WindowStyle = ProcessWindowStyle.Hidden;
Process.Start(p1);
使用下面的代码,获取安卓内置或外置SD卡根目录:
//内置sd卡路径
String sdcardPath = System.getenv("EXTERNAL_STORAGE");
//内置sd卡路径
String sdcardPath = Environment.getExternalStorageDirectory().getAbsolutePath();
//外置sd卡路径
String extSdcardPath = System.getenv("SECONDARY_STORAGE");
如果是继承activity
,则
requestWindowFeature(Window.FEATURE_NO_TITLE) //隐藏标题
如果是继承AppCompatActivity
, 则
supportActionBar?.hide()
使用下面的代码,可以实现C#执行DOS命令,并返回DOS命令的输出:
/// <summary>
/// 执行DOS命令,返回DOS命令的输出
/// </summary>
/// <param name="dosCommand">dos命令</param>
/// <param name="milliseconds">等待命令执行的时间(单位:毫秒),
/// 如果设定为0,则无限等待</param>
/// <returns>返回DOS命令的输出</returns>
public static string Execute(string command, int seconds)
{
string output = ""; //输出字符串
if (command != null && !command.Equals(""))
{
Process process = new Process();//创建进程对象
ProcessStartInfo startInfo = new ProcessStartInfo();
startInfo.FileName = "cmd.exe";//设定需要执行的命令
startInfo.Arguments = "/C " + command;//“/C”表示执行完命令后马上退出
startInfo.UseShellExecute = false;//不使用系统外壳程序启动
startInfo.RedirectStandardInput = false;//不重定向输入
startInfo.RedirectStandardOutput = true; //重定向输出
startInfo.CreateNoWindow = true;//不创建窗口
process.StartInfo = startInfo;
try
{
if (process.Start())//开始进程
{
if (seconds == 0)
{
process.WaitForExit();//这里无限等待进程结束
}
else
{
process.WaitForExit(seconds); //等待进程结束,等待时间为指定的毫秒
}
output = process.StandardOutput.ReadToEnd();//读取进程的输出
}
}
catch (Exception ex)
{
Console.WriteLine(ex.Message);//捕获异常,输出异常信息
}
finally
{
if (process != null)
process.Close();
}
}
return output;
}
asp.net的开发中,数据库连接信息一般都在是web.config中配置的,配置方法如下:
<connectionStrings>
<add name="conn" connectionString="Data Source=123.206.101.218;Initial Catalog=MyShop;Persist Security Info=True;User ID=sa;Password=123456" providerName="System.Data.SqlClient" />
</connectionStrings>
调用方法:
using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data.SqlClient;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Web;
namespace MyShop
{
class Db
{
public static SqlConnection GetConnection()
{
var connectionString = System.Configuration.ConfigurationManager.ConnectionStrings["conn"].ConnectionString;
var conn = new SqlConnection(connectionString);
return conn;
}
}
}