csharp-string

发表于 2020-06-15 更新于 2022-11-10 分类于 Language 阅读次数：本文字数： 9.9k 阅读时长 ≈ 9 分钟

修饰符

$ before string

// $ is short-hand for String.Format and is used with string interpolations,
// which is a new feature of C# 6. As used in your case, it does nothing, just as string.Format() would do nothing.

var anInt = 1;
var aBool = true;
var aString = "3";
var aFloat = 12.3456
var formated = string.Format("{0},{1},{2}", anInt, aBool, aString);

// same result
var formated = $"{anInt},{aBool},{aString},{aFloat:f2}";
aFloat = 12.34

// 16进制转换
tb_test.Text = $"{it1:X}";

@ before string

//避免转义字符
// before
"\\\\servername\\share\\folder"

// after
@"\\servername\share\folder"

原始字符串

以至少三个双引号字符序列 (“””) 开头和结尾。可以使用三个以上的连续字符开始和结束序列，以支持包含三个（或更多）重复引号字符的字符串字面量。
单行原始字符串字面量需要左引号和右引号字符位于同一行上。
多行原始字符串字面量需要左引号和右引号字符位于各自的行上。
在多行原始字符串字面量中，会删除右引号左侧的任何空格。

string embeddedXML = """
       <element attr = "content">
           <body style="normal">
               Here is the main text
           </body>
           <footer>
               Excerpts from "An amazing story"
           </footer>
       </element >
       """;

byte[] 复制

Buffer.BlockCopy(srcArray, 0, dstArray, 0, srcArray.Length);
Array.Copy(src, dest, src.Length);

byte[] to string

string stringToConvert = "123456789abcd";
byte[] buffer = Encoding.UTF8.GetBytes(stringToConvert);
Buffer.BlockCopy(buffer, 0, rData, 0, buffer.Length);

int count = rData.Count(bt => bt != 0);//find the first null
string converted = System.Text.Encoding.ASCII.GetString(rData,0, count);
//  string converted = Encoding.UTF8.GetString(rData, 0, rData.Length);

clear byte[]

Array.Clear(rData, 0, rData.Length);

删除

protocol.Param.Replace("+", string.Empty);

去掉结尾字符

s=s.TrimEnd(',')

string hex byte[]

public static string ByteArrayToString(byte[] ba)
{
    return BitConverter.ToString(ba).Replace("-", "");
}

public static byte[] StringToByteArray(String hex)
{
    int NumberChars = hex.Length;
    byte[] bytes = new byte[NumberChars / 2];
    for (int i = 0; i < NumberChars; i += 2)
        bytes[i / 2] = Convert.ToByte(hex.Substring(i, 2), 16);
    return bytes;
}

string author = "Mahesh Chand";  
// Convert a C# string to a byte array  
byte[] bytes = Encoding.ASCII.GetBytes(author);  
foreach ( byte b in bytes)  
{  
   Console.WriteLine(b);  
}

// Convert a byte array to a C# string. 
string str = Encoding.ASCII.GetString(bytes);  
Console.WriteLine(str);

数字转字符串

int varInt = 1;
string varString = Convert.ToString(varInt);
string varString2 = varInt.ToString();

// C# 提供了下列内置的类型转换方法
ToDateTime
把类型（整数或字符串类型）转换为 日期-时间 结构。
ToDouble
把类型转换为双精度浮点型。

精度

// just two decimal places
String.Format("{0:0.00}", 123.4567);      // "123.46"
String.Format("{0:0.00}", 123.4);         // "123.40"
String.Format("{0:0.00}", 123.0);         // "123.00"

// max. two decimal places
String.Format("{0:0.##}", 123.4567);      // "123.46"
String.Format("{0:0.##}", 123.4);         // "123.4"
String.Format("{0:0.##}", 123.0);         // "123"

// at least two digits before decimal point
String.Format("{0:00.0}", 123.4567);      // "123.5"
String.Format("{0:00.0}", 23.4567);       // "23.5"
String.Format("{0:00.0}", 3.4567);        // "03.5"
String.Format("{0:00.0}", -3.4567);       // "-03.5"

String.Format("{0:0,0.0}", 12345.67);     // "12,345.7"
String.Format("{0:0,0}", 12345.67);       // "12,346"

String.Format("{0:0.0}", 0.0);            // "0.0"
String.Format("{0:0.#}", 0.0);            // "0"
String.Format("{0:#.0}", 0.0);            // ".0"
String.Format("{0:#.#}", 0.0);            // ""

String.Format("{0,10:0.0}", 123.4567);    // "     123.5"
String.Format("{0,-10:0.0}", 123.4567);   // "123.5     "
String.Format("{0,10:0.0}", -123.4567);   // "    -123.5"
String.Format("{0,-10:0.0}", -123.4567);  // "-123.5    "

String.Format("{0:0.00;minus 0.00;zero}", 123.4567);   // "123.46"
String.Format("{0:0.00;minus 0.00;zero}", -123.4567);  // "minus 123.46"
String.Format("{0:0.00;minus 0.00;zero}", 0.0);        // "zero"

String.Format("{0:my number is 0.0}", 12.3);   // "my number is 12.3"
String.Format("{0:0aaa.bbb0}", 12.3);          // "12aaa.bbb3"

大量数组转字符串

// 这个效率很低 下面同样的数据 28.423ms
int[] val = ...
var Param = string.Join(",", val);

// 这个花费 0.2839ms
StringBuilder stringBuilder = new StringBuilder();
using (StreamWriter streamWriter = new StreamWriter(@"d:\a.csv", false, Encoding.GetEncoding("utf-16")))
{
    foreach (var it in data)
    {
        for (var i = 6; i < 3200+6; ++i)
        {
            // 一次性多个数据 反而慢了 用了 2ms
            //stringBuilder.AppendFormat("{0},{0},{0},{0},{0},{0},{0},{0},{0},{0},", val[i], val[i+1], val[i+2], val[i+3], val[i+4], val[i+5], val[i+6], val[i+7], val[i+8], val[i+9]);
            stringBuilder.AppendFormat("{0},", it[i]);
        }
        streamWriter.WriteLine(stringBuilder);
    }
    // 去掉最后一个字符
    stringBuilder.Length--;
}

//清空
stringBuilder.Length = 0;

String [] items={"Jan","Feb","Mar"};
 StringBuilder sb=new StringBuilder();
 foreach(var entity in items)
 {
   sb.Append(entity + Environment.NewLine);
 }
 Textbox1.Text=sb.tostring();

float int 互转

unsafe
{
    float s = (float)3.194;
    void* vp = &s;
    // 轮廓仪默认是 0.01um， 这里转换成毫米
    int i1 = (*(int*)vp);
    float ss = (*(float*)&i1);
    Console.WriteLine($"i={i1},ss={ss}");

}

int to byte[]

byte[] bytes = BitConverter.GetBytes(i);

byte[] to int

int iVal = BitConverter.ToInt32(rData, 0);

字符串转数字

如果确定字符串中是可以转成数字的字符，可以用int.Parse(string s)，该语句返回的是转换得到的int值;
如果不能确定字符串是否可以转成数字，可以用int.TryParse(string s, out int result),该语句返回的是bool值，指示转换操作是否成功，参数result是存放转换结果的变量。

string str = string.Empty;
str = "123";
int result=int.Parse(str);

string str = string.Empty;
str = "xyz";
int result;
int.TryParse(str, out result);

string prefixedHex = "0x142CBD";
// this works, and returns 1322173
int intValue = Convert.ToInt32(prefixedHex , 16);

判断字母，数字

if (false == char.IsLetterOrDigit(elaboration[pos-1]))
{
    isReplace = 1;
}

查找

Indexof(Char C):  找到第一个字符c的index，如果没找到返回-1
Indexof(string str):  找到str的index，如果没找到返回-1
LastIndexof(string str):  返回当前字符或字符串的最后一个匹配项位置


char[] chars = { '$', 'C', 'S', 'D' };
if (-1 != protocol.Param.IndexOfAny(chars))
{
    Log.Warning($"发现非期望数据:{str}");
    continue;
}

格式化

website

// int to string
String.Format("k{0}",m_db.m_coeffs.Count + 1)

$ - string interpolation

msdn

比 format 更具可读性

var f = 123.456;
var s = $"{f:0.00}";

// 前面补 0
int pulseInterval = 5;
var msg = $"{pulseInterval:D8}"; 
// msg is "00000005"

string name = "Mark";
var date = DateTime.Now;

// Composite formatting:
Console.WriteLine("Hello, {0}! Today is {1}, it's {2:HH:mm} now.", name, date.DayOfWeek, date);
// String interpolation:
Console.WriteLine($"Hello, {name}! Today is {date.DayOfWeek}, it's {date:HH:mm} now.");
// Both calls produce the same output that is similar to:
// Hello, Mark! Today is Wednesday, it's 19:40 now.

int count = 10
string msg = $"{msgIn}+{count:d03}";

字符转字符串

for (int i = 0; i < 12; i++)
{
    m_dateMapping.Add(new ModelDateMapping
    {
        CurDate = $"{i + 1}",
        CurDateMapString = ((char)('A' + i)).ToString()
    });
    Insert_model<ModelDateMapping>(m_dateMapping[0]);
}

split

string[] lines = theText.Split(
    new[] { Environment.NewLine },
    StringSplitOptions.None
);


string[] lines = theText.Split(new[] { "\r\n", "\r", "\n" },StringSplitOptions.None);

string[] to List

string s = [...]
var str_list = s.split(",").ToList();

正则表达式

string formular = "(-t4-t6-t8)/3";
var matches = Regex.Matches(formular, "t[0-9]+?");
foreach (var match in matches)
{
    // match.Value will contain one of the matches e.g. t4, t6,t8
    string s = match.ToString();
}

//判断完整词 \b

// 找到 mv 整个词，然后替换为 mvN  N 对应项目编号
var record = Regex.Replace(formula, @"\b(mv)\b", $"mv{item.No}", RegexOptions.IgnorePatternWhitespace);

convert utf8 gbk

in .NET. All strings in .NET are effectively UTF-16.However, .NET provides the Encoding class to allow you to decode binary data into strings, and re-encode it later.

var encParam = EncodingConvert(protocol.Param, Encoding.GetEncoding("Unicode"), Encoding.GetEncoding("gb2312"));
public string EncodingConvert(string fromString, Encoding fromEncoding, Encoding toEncoding)
{
    byte[] fromBytes = fromEncoding.GetBytes(fromString);
    byte[] toBytes = Encoding.Convert(fromEncoding, toEncoding, fromBytes);

    string toString = toEncoding.GetString(toBytes);
    return toString;
}

public string Utf8ToGB2312(string utf8String)
{
    Encoding fromEncoding = Encoding.UTF8;
    Encoding toEncoding = Encoding.GetEncoding("gb2312");
    return EncodingConvert(utf8String, fromEncoding, toEncoding);
}

public string GB2312ToUtf8(string gb2312String)
{
    Encoding fromEncoding = Encoding.GetEncoding("gb2312");
    Encoding toEncoding = Encoding.UTF8;
    return EncodingConvert(gb2312String, fromEncoding, toEncoding);
}

.net core gb2312 不支持

System.Text.EncodingProvider provider = System.Text.CodePagesEncodingProvider.Instance;
Encoding.RegisterProvider(provider);

拼接

Using + operator
String Interpolation
String.Concatenate() method
String.Join() method
String.Format() method
StringBuilder.Append() method

private StringBuilder strDatas = new StringBuilder();

strDatas.Append(str);
strDatas.Clear();
strDatas.ToString();

// 每个成员间添加 ，
string.Join(",", yourCollection)

// 
string strDatas = "";
StringBuilder strBuilder = new StringBuilder();
// 准备字符串类型的 csv 格式数据
foreach (var it in datas)
{
    foreach (var data in it)
    {
        strBuilder.Append(String.Format("{0:0.0000},", data));
    }
    // 去掉最后一个字符
    --strBuilder.Length;
    strBuilder.Append("\n");
}
strDatas += strBuilder.ToString();