我一直在寻找int.TryParse方法实现，它实际上是如何工作的，但我还没有找到。我必须知道，关于string，它是否是一个数值，但我现在不想转换它。
所以我只需要来自bool的{{1}}结果。所以问题是：
int.TryParse结果的功能和
bool实际上是如何运作的（内部是int.TryParse还是遍历输入try ... catch的字符？）答案 0 :(得分：91)
如果您只需要bool结果，只需使用返回值并忽略out参数。
bool successfullyParsed = int.TryParse(str, out ignoreMe);
if (successfullyParsed){
// ...
}
修改：同时您还可以查看original source code：
如果我想知道某些内容是如何实现的，我正在使用ILSpy来反编译.NET代码。
结果如下：
// int
/// <summary>Converts the string representation of a number to its 32-bit signed integer equivalent. A return value indicates whether the operation succeeded.</summary>
/// <returns>true if s was converted successfully; otherwise, false.</returns>
/// <param name="s">A string containing a number to convert. </param>
/// <param name="result">When this method returns, contains the 32-bit signed integer value equivalent to the number contained in s, if the conversion succeeded, or zero if the conversion failed. The conversion fails if the s parameter is null, is not of the correct format, or represents a number less than <see cref="F:System.Int32.MinValue"></see> or greater than <see cref="F:System.Int32.MaxValue"></see>. This parameter is passed uninitialized. </param>
/// <filterpriority>1</filterpriority>
public static bool TryParse(string s, out int result)
{
return Number.TryParseInt32(s, NumberStyles.Integer, NumberFormatInfo.CurrentInfo, out result);
}
// System.Number
internal unsafe static bool TryParseInt32(string s, NumberStyles style, NumberFormatInfo info, out int result)
{
byte* stackBuffer = stackalloc byte[1 * 114 / 1];
Number.NumberBuffer numberBuffer = new Number.NumberBuffer(stackBuffer);
result = 0;
if (!Number.TryStringToNumber(s, style, ref numberBuffer, info, false))
{
return false;
}
if ((style & NumberStyles.AllowHexSpecifier) != NumberStyles.None)
{
if (!Number.HexNumberToInt32(ref numberBuffer, ref result))
{
return false;
}
}
else
{
if (!Number.NumberToInt32(ref numberBuffer, ref result))
{
return false;
}
}
return true;
}
不，我在路上看不到任何Try-Catchs：
// System.Number
private unsafe static bool TryStringToNumber(string str, NumberStyles options, ref Number.NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
{
if (str == null)
{
return false;
}
fixed (char* ptr = str)
{
char* ptr2 = ptr;
if (!Number.ParseNumber(ref ptr2, options, ref number, numfmt, parseDecimal) || ((ptr2 - ptr / 2) / 2 < str.Length && !Number.TrailingZeros(str, (ptr2 - ptr / 2) / 2)))
{
return false;
}
}
return true;
}
// System.Number
private unsafe static bool ParseNumber(ref char* str, NumberStyles options, ref Number.NumberBuffer number, NumberFormatInfo numfmt, bool parseDecimal)
{
number.scale = 0;
number.sign = false;
string text = null;
string text2 = null;
string str2 = null;
string str3 = null;
bool flag = false;
string str4;
string str5;
if ((options & NumberStyles.AllowCurrencySymbol) != NumberStyles.None)
{
text = numfmt.CurrencySymbol;
if (numfmt.ansiCurrencySymbol != null)
{
text2 = numfmt.ansiCurrencySymbol;
}
str2 = numfmt.NumberDecimalSeparator;
str3 = numfmt.NumberGroupSeparator;
str4 = numfmt.CurrencyDecimalSeparator;
str5 = numfmt.CurrencyGroupSeparator;
flag = true;
}
else
{
str4 = numfmt.NumberDecimalSeparator;
str5 = numfmt.NumberGroupSeparator;
}
int num = 0;
char* ptr = str;
char c = *ptr;
while (true)
{
if (!Number.IsWhite(c) || (options & NumberStyles.AllowLeadingWhite) == NumberStyles.None || ((num & 1) != 0 && ((num & 1) == 0 || ((num & 32) == 0 && numfmt.numberNegativePattern != 2))))
{
bool flag2;
char* ptr2;
if ((flag2 = ((options & NumberStyles.AllowLeadingSign) != NumberStyles.None && (num & 1) == 0)) && (ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
{
num |= 1;
ptr = ptr2 - (IntPtr)2 / 2;
}
else
{
if (flag2 && (ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
{
num |= 1;
number.sign = true;
ptr = ptr2 - (IntPtr)2 / 2;
}
else
{
if (c == '(' && (options & NumberStyles.AllowParentheses) != NumberStyles.None && (num & 1) == 0)
{
num |= 3;
number.sign = true;
}
else
{
if ((text == null || (ptr2 = Number.MatchChars(ptr, text)) == null) && (text2 == null || (ptr2 = Number.MatchChars(ptr, text2)) == null))
{
break;
}
num |= 32;
text = null;
text2 = null;
ptr = ptr2 - (IntPtr)2 / 2;
}
}
}
}
c = *(ptr += (IntPtr)2 / 2);
}
int num2 = 0;
int num3 = 0;
while (true)
{
if ((c >= '0' && c <= '9') || ((options & NumberStyles.AllowHexSpecifier) != NumberStyles.None && ((c >= 'a' && c <= 'f') || (c >= 'A' && c <= 'F'))))
{
num |= 4;
if (c != '0' || (num & 8) != 0)
{
if (num2 < 50)
{
number.digits[(IntPtr)(num2++)] = c;
if (c != '0' || parseDecimal)
{
num3 = num2;
}
}
if ((num & 16) == 0)
{
number.scale++;
}
num |= 8;
}
else
{
if ((num & 16) != 0)
{
number.scale--;
}
}
}
else
{
char* ptr2;
if ((options & NumberStyles.AllowDecimalPoint) != NumberStyles.None && (num & 16) == 0 && ((ptr2 = Number.MatchChars(ptr, str4)) != null || (flag && (num & 32) == 0 && (ptr2 = Number.MatchChars(ptr, str2)) != null)))
{
num |= 16;
ptr = ptr2 - (IntPtr)2 / 2;
}
else
{
if ((options & NumberStyles.AllowThousands) == NumberStyles.None || (num & 4) == 0 || (num & 16) != 0 || ((ptr2 = Number.MatchChars(ptr, str5)) == null && (!flag || (num & 32) != 0 || (ptr2 = Number.MatchChars(ptr, str3)) == null)))
{
break;
}
ptr = ptr2 - (IntPtr)2 / 2;
}
}
c = *(ptr += (IntPtr)2 / 2);
}
bool flag3 = false;
number.precision = num3;
number.digits[(IntPtr)num3] = '\0';
if ((num & 4) != 0)
{
if ((c == 'E' || c == 'e') && (options & NumberStyles.AllowExponent) != NumberStyles.None)
{
char* ptr3 = ptr;
c = *(ptr += (IntPtr)2 / 2);
char* ptr2;
if ((ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
{
c = *(ptr = ptr2);
}
else
{
if ((ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
{
c = *(ptr = ptr2);
flag3 = true;
}
}
if (c >= '0' && c <= '9')
{
int num4 = 0;
do
{
num4 = num4 * 10 + (int)(c - '0');
c = *(ptr += (IntPtr)2 / 2);
if (num4 > 1000)
{
num4 = 9999;
while (c >= '0' && c <= '9')
{
c = *(ptr += (IntPtr)2 / 2);
}
}
}
while (c >= '0' && c <= '9');
if (flag3)
{
num4 = -num4;
}
number.scale += num4;
}
else
{
ptr = ptr3;
c = *ptr;
}
}
while (true)
{
if (!Number.IsWhite(c) || (options & NumberStyles.AllowTrailingWhite) == NumberStyles.None)
{
bool flag2;
char* ptr2;
if ((flag2 = ((options & NumberStyles.AllowTrailingSign) != NumberStyles.None && (num & 1) == 0)) && (ptr2 = Number.MatchChars(ptr, numfmt.positiveSign)) != null)
{
num |= 1;
ptr = ptr2 - (IntPtr)2 / 2;
}
else
{
if (flag2 && (ptr2 = Number.MatchChars(ptr, numfmt.negativeSign)) != null)
{
num |= 1;
number.sign = true;
ptr = ptr2 - (IntPtr)2 / 2;
}
else
{
if (c == ')' && (num & 2) != 0)
{
num &= -3;
}
else
{
if ((text == null || (ptr2 = Number.MatchChars(ptr, text)) == null) && (text2 == null || (ptr2 = Number.MatchChars(ptr, text2)) == null))
{
break;
}
text = null;
text2 = null;
ptr = ptr2 - (IntPtr)2 / 2;
}
}
}
}
c = *(ptr += (IntPtr)2 / 2);
}
if ((num & 2) == 0)
{
if ((num & 8) == 0)
{
if (!parseDecimal)
{
number.scale = 0;
}
if ((num & 16) == 0)
{
number.sign = false;
}
}
str = ptr;
return true;
}
}
str = ptr;
return false;
}
答案 1 :(得分：15)
仅仅因为int.TryParse给你的价值并不意味着你需要保留它;你可以很高兴地这样做：
int temp;
if (int.TryParse(inputString, out temp))
{
// do stuff
}
如果您不需要，可以完全忽略temp。如果你确实需要它，那么嘿，它会在你想要的时候等着你。
至于内部，据我记得它试图将字符串的原始字节读作int并测试结果是否有效，或者某些东西;它不像迭代寻找非数字字符那么简单。
答案 2 :(得分：10)
我们现在可以在C＃7.0及以上版本中写道：
if (int.TryParse(inputString, out _))
{
//do stuff
}
答案 3 :(得分：7)
编译正则表达式，因此速度创建一次并重复使用它 新的比IsMatch需要更长的时间 这只检查所有数字 它不检查范围 如果您需要测试范围，那么TryParse就是您的选择。
private static Regex regexInt = new Regex("^\\d+$");
static bool CheckReg(string value)
{
return regexInt.IsMatch(value);
}
答案 4 :(得分：7)
TryParse是单行解析或验证的最佳方式：
int nCurPage = int.TryParse(txtPageNo.Text, out nCurPage) ? nCurPage : 1;
// or
int nCurPage = !int.TryParse(txtPageNo.Text, out nCurPage) ? 1 : nCurPage;
答案 5 :(得分：3)
检查此简单程序以了解int.TryParse
class Program
{
static void Main()
{
string str = "7788";
int num1;
bool n = int.TryParse(str, out num1);
Console.WriteLine(num1);
Console.ReadLine();
}
}
输出为：7788