当字符串中有大写字符或下划线时，我想添加一个空格。
我该怎么做？
示例 1
输入
ThisIsAnInputString
输出（结果）
This Is An Input String
示例 2
输入
This_Is_An_Input_String
输出（结果）
This Is An Input String
【问题讨论】：
您可以使用一个正则表达式来匹配一个小写字符后跟一个大写字符，中间有一个可选的下划线：
string output = Regex.Replace(input, "([a-z])_?([A-Z])", "$1 $2");
您可能还想用它来处理单个字符的单词：
string output = Regex.Replace(input, "(?<!^)_?([A-Z])", " $1");
【讨论】：
[a-z] 更改为[a-zA-Z] 以处理ThisIsATest 之类的字符串。
[a-z]? 就足够了。即：Regex.Replace(input, "([a-z]?)_?([A-Z])", "$1 $2")。 This_Is_A_Test 在您的示例中不会产生预期的结果。
add a space when an uppercase character。这也包括第一个字符。
下划线：
string inputString = "This_Is_An_Input_String";
string resultString = inputString.Replace('_', ' ');
首都：
string inputString = "ThisIsAnInputString";
//this will put a space before all capitals that are preceded by a lowercase character
string resultString = Regex.Replace(inputString, @"([a-z])([A-Z])", "$1 $2");
【讨论】：
根据您的规范，您希望在任何大写字符之前添加一个空格。这也应该适用于第一个字母。所有下划线都应替换为空格。这里的大多数答案都省略了第一个空格（This 之前）。
var pattern = "([a-z?])[_ ]?([A-Z])";
var input = "ThisIsATest";
var output = Regex.Replace(input, pattern, "$1 $2");
// output = " This Is A Test"
var input = "This_Is_A_Test";
var output = Regex.Replace(input, pattern, "$1 $2");
// output = " This Is A Test"
var input = "ThisIsAnInputString";
var output = Regex.Replace(input, pattern, "$1 $2");
// output = " This Is An Input String"
var input = "This_Is_An_Input_String";
var output = Regex.Replace(input, pattern, "$1 $2");
// output = " This Is An Input String"
如果您不想在开头添加 额外 空格，请使用TrimStart
var input = "This_Is_A_Test";
var output = Regex.Replace(input, pattern, "$1 $2").TrimStart(' ');
// output = "This Is A Test"
编辑（更新）：
我已将不同的正则表达式建议编译成一个小型测试应用程序来验证结果：
static void Main(string[] args)
{
const string expectedResult = "This Is A Test";
var samples = new string[][]
{
new [] {"This Is A Test", "This Is A Test"},
new [] {"ThisIsATest", "This Is A Test"},
new [] {"This_Is_A_Test", "This Is A Test"},
new [] {"ThisIsA_Test", "This Is A Test"},
new [] {"This_IsATest", "This Is A Test"},
new [] {"_ThisIsATest", "This Is A Test"},
new [] {"_This_Is_A_Test", "This Is A Test"},
new [] {"Thi_s_Is_A_Test", "Thi s Is A Test"},
new [] {"T hi_s_Is_A_Te s_ t", "T hi s Is A Te s t"}
};
foreach (var input in samples)
{
Console.WriteLine(input[0] + " => " + input[1]);
// Guffa 1 1/9 correct.
Console.WriteLine("Guffa 1: " + (Regex.Replace(input[0], @"([a-z])_?([A-Z])", "$1 $2") == input[1]));
// Guffa 2 4/9 correct.
Console.WriteLine("Guffa 2: " + (Regex.Replace(input[0], @"(?<!^)_?([A-Z])", " $1") == input[1]));
// Abe Miesler 1/9 correct.
Console.WriteLine("Abe Miesler: " + (Regex.Replace(input[0], @"([a-zA-Z])_?([A-Z])", "$1 $2") == input[1]));
// AppDeveloper 2/9 correct. (Not entirely fair since it was not meant for underscores).
Console.WriteLine("AppDeveloper: " + (Regex.Replace(input[0], @"_([A-Z])", " $1") == input[1]));
// sparky68967 1/9 correct. (Not entirely fair since it was not meant for underscores).
Console.WriteLine("sparky68967: " + (Regex.Replace(input[0], @"([a-z])([A-Z])", "$1 $2") == input[1]));
// p.s.w.g 4/9 correct.
Console.WriteLine("p.s.w.g: " + (Regex.Replace(Regex.Replace(input[0], @"([A-Z]+)([A-Z][a-z])", "$1_$2"), "_", " ") == input[1]));
// Sani Huttunen 1 7/9 correct.
Console.WriteLine("Sani Huttunen 1: " + (Regex.Replace(input[0], @"([a-z]?)[_ ]?([A-Z])", "$1 $2").TrimStart(' ') == input[1]));
// Sani Huttunen 2 9/9 correct.
Console.WriteLine("Sani Huttunen 2: " + (Regex.Replace(input[0].Replace('_', ' '), @"(?<!^)[ ]?([A-Z])", " $1").TrimStart(' ') == input[1]));
Console.WriteLine();
}
}
【讨论】：
^ 字符？
对于输入类型：ThisIsAnInputString
string input1 = "ThisIsAnInputString";
StringBuilder builder = new StringBuilder();
foreach (char c in input1)
{
if (Char.IsUpper(c))
{
builder.Append(' ');
builder.Append(c);
}
else
{
builder.Append(c);
}
}
string output = builder.ToString().Trim();
对于输入类型：This_Is_An_Input_String
string input2 = "This_Is_An_Input_String";
string output = Regex.Replace(input2, "_([A-Z])", " $1");
【讨论】：
// check if string is empty
if (string.IsNullOrEmpty(input))
return string.Empty;
if (input.Contains('_'))
{
return input.Replace('_', ' ');
}
else
{
StringBuilder newString = new StringBuilder();
foreach (Char char1 in input)
{
if (char.IsUpper(char1))
newString.Append(new char[] { ' ', char1 });
else
newString.Append(char1);
}
newString.Remove(0, 1);
return newString.ToString();
}
【讨论】：
static void Main(string[] args)
{
String str = "ThisIsAnInputString";
String str2 = "This_Is_An_Input_String";
Console.WriteLine(str);
Console.WriteLine(str2);
StringBuilder sb = new StringBuilder();
StringBuilder sb2 = new StringBuilder();
str.ToCharArray().ToList().ForEach(c => sb.Append(c == '_' ? " " : char.IsLower(c) ? c.ToString() : " " + c.ToString()));
str2.ToCharArray().ToList().ForEach(c => sb2.Append(c == '_' ? " " : char.IsLower(c) ? c.ToString() : " " + c.ToString()));
str = sb.ToString().Trim(" ".ToCharArray());
str2 = sb2.ToString().Trim(" ".ToCharArray());
Console.WriteLine(str);
Console.WriteLine(str2);
Console.Read();
}
【讨论】：