我有一个要多次操作的字符串生成器，我需要用不同长度的字符串替换其中的字符串。
sb = new StringBuilder("This has {Count} Values. Your search was '{SearchText}'. Did you mean '{DidYouMean}'?")
//get the replacement areas, this would search for the field names within {}
MatchCollection matches = GetReplacementAreas(sb);
int indexOffset=0;
foreach(Match m in matches)
{
//fields is a dictionary containing keys that match the fields
sb.ReplaceAt(m.Index,m.Length,fields[m.Value]);
}
显然 ReplaceAt 不存在。我要自己写了。其他人已经这样做了吗？
public static class StringBuilderExtensions
{
#if EXTENSIONS_SUPPORTED
public static StringBuilder ReplaceAt(this StringBuilder sb, string value, int index, int count)
{
return StringBuilderExtensions.ReplaceAt(sb, value, index, count);
}
#endif
public static StringBuilder ReplaceAt(StringBuilder sb, string value, int index, int count)
{
if (value == null)
{
sb.Remove(index, count);
}
else
{
int lengthOfValue = value.Length;
if (lengthOfValue > count)
{
string valueToInsert = value.Substring(count);
sb.Insert(index + count, valueToInsert);
}
if (lengthOfValue < count)
{
sb.Remove(index + count, lengthOfValue - count);
}
char[] valueChars = value.ToCharArray();
for (int i = 0; i < lengthOfValue; i++)
{
sb[index + i] = valueChars[i];
}
}
return sb;
}
}
为了准确起见，enorl76 答案看起来很有希望，但不适用于 Unicode 字符串，特别是 2 字节宽度的 Unicode 字符。这是在.Net Fiddle中模拟的 enorl76 答案以供考试。
这是解决此问题的一个实现，此处为 .Net Fiddle 。
using System.Linq;
using System.Diagnostics;
using System;
using System.Text;
using System.Globalization;
//Created for
//http://metadataconsulting.blogspot.com/2019/03/A-Unicode-ReplaceAt-string-extension-method-handles-Unicode-string-properly.html
public static class Program
{
const char cEMPTY = '\0';
static readonly string EMPTY = cEMPTY.ToString();
public static string UnicodeReplaceAt(this string str, int offset, char replaceChar)
{
int count = 1; //number of times to replace
string replaceBy = replaceChar.ToString();
return new StringInfo(str).ReplaceByPosition(replaceBy, offset, count).String;
}
public static StringInfo ReplaceByPosition(this StringInfo str, string replaceBy, int offset, int count)
{
if (replaceBy != EMPTY)
return str.RemoveByTextElements(offset, count).InsertByTextElements(offset, replaceBy);
else
return str.RemoveByTextElements(offset, count);
}
public static StringInfo RemoveByTextElements(this StringInfo str, int offset, int count)
{
//Tue 20-Aug-19 11:32am metadataconsulting.ca - replaceat index > string.len return orginal string
if (offset > str.LengthInTextElements)
return str;
return new StringInfo(string.Concat(
str.SubstringByTextElements(0, offset),
offset + count < str.LengthInTextElements
? str.SubstringByTextElements(offset + count, str.LengthInTextElements - count - offset)
: string.Empty
));
}
public static StringInfo InsertByTextElements(this StringInfo str, int offset, string insertStr)
{
//Tue 20-Aug-19 11:32am metadataconsulting.ca - replaceat index > string.len return orginal string
if (offset > str.LengthInTextElements)
return str;
if (string.IsNullOrEmpty(str.String))
return new StringInfo(insertStr);
return new StringInfo(string.Concat(
str.SubstringByTextElements(0, offset),
insertStr,
str.LengthInTextElements - offset > 0 ? str.SubstringByTextElements(offset, str.LengthInTextElements - offset) : ""
));
}
public static string SubsituteStringStringBuilder(this string s, int idx, char replaceChar)
{
if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)
return s;
return new StringBuilder(s).Remove(idx, 1).Insert(idx, replaceChar.ToString()).ToString();
}
public static string ReplaceAtSubstring(this string s, int idx, char replaceChar)
{
if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)
return s;
return s.Substring(0, idx) + replaceChar.ToString() + s.Substring(idx + replaceChar.ToString().Length, s.Length - (idx + replaceChar.ToString().Length));
}
public static string ReplaceAtStringManipulation(this string s, int idx, char replaceChar)
{
if (string.IsNullOrEmpty(s) || idx >= s.Length || idx < 0)
return s;
return s.Remove(idx, 1).Insert(idx, replaceChar.ToString());
}
public static string ReplaceAtLinq(this string value, int index, char newchar)
{
if (value.Length <= index)
return value;
else
return string.Concat(value.Select((c, i) => i == index ? newchar : c));
}
public static string ReplaceAtCharArray(this string input, uint index, char newChar)
{
if (string.IsNullOrEmpty(input) || index >= input.Length)
return input;
char[] chars = input.ToCharArray();
chars[index] = newChar;
return new string(chars);
}
public static void Main()
{
//In .NET 4.5 and later also UTF-16 is supported
//Console.OutputEncoding = System.Text.Encoding.Unicode;
//é Latin Small Letter e with Acute U+00E9 - single byte Unicode character
// Smiling Face with Smiling Eyes Emoji U+1F60A - double byte Unicode character
// Multiple Musical Notes Emoji U+1F3B6 - - double byte Unicode character
// Fire Emoji U+1F525 -- double byte Unicode character
Console.WriteLine("Unicode String Replace At Issue");
Console.WriteLine("Lets examine string \"é-\"");
Console.WriteLine("é- is length of " + "é-".Length + ", but there are ONLY 4 characters! Why not len=4?");
Console.WriteLine(" are double byte UNICODE characters (> \\u10000) of width or len 2 each ");
Console.WriteLine("é- below will replace space after lasting character '-' (position 4) with a sub using most common techniques seen online");
Console.WriteLine();
Stopwatch sw = new Stopwatch();
sw.Start();
Console.WriteLine("é- using ReplaceAtCharArray".ReplaceAtCharArray(4, 'X'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.WriteLine("é- using ReplaceAtLinq".ReplaceAtLinq(4, 'Y'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.WriteLine("é- using ReplaceAtStringManipulation".ReplaceAtStringManipulation(4, 'Z'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.WriteLine("é- using ReplaceAtSubstring".ReplaceAtSubstring(4, 'A'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.WriteLine("é- using SubsituteStringStringBuilder".SubsituteStringStringBuilder(4, 'W'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.WriteLine("é- using UnicodeReplaceAt".UnicodeReplaceAt(4, '4'));
sw.Stop();
Console.WriteLine("in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
Console.WriteLine();
Console.WriteLine("UnicodeReplaceAt replaces properly at position 4 in zero based index string");
Console.WriteLine();
sw.Restart();
Console.Write("é- using UnicodeReplaceAt(0, '0')".UnicodeReplaceAt(0, '0'));
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.Write("é- using UnicodeReplaceAt(1, '1')".UnicodeReplaceAt(1, '1'));
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.Write("é- using UnicodeReplaceAt(2, '2')".UnicodeReplaceAt(2, '2'));
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.Write("é- using UnicodeReplaceAt(3, '3')".UnicodeReplaceAt(3, '3'));
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
sw.Restart();
Console.Write("é- using UnicodeReplaceAt(4, '4')".UnicodeReplaceAt(4, '4'));
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
Console.Write("é-".UnicodeReplaceAt(5, '5')+" using UnicodeReplaceAt(5, '5') - this is beyond end of string, so return orginal string");
sw.Stop();
Console.WriteLine(" in {0} ticks.", sw.ElapsedTicks.ToString("N0"));
Console.WriteLine();
Console.WriteLine("String.Replace works, but replaces all characters, not at specific location as above functions");
Console.WriteLine();
Console.Write("é- using String.Replace".Replace("", "+") + "('', '+')");
}
}