我做了一些小改变@ theecodeking的回答。

似乎;

对于int类型，最快的方法是TryParse

对于长类型最快的方法是正则表达式。

我的结果如下(打勾)

For int:

TryParse Max: 355788
IsDigitsOnly Max: 787013
Regex Max: 1297691

TryParse Avg: 186007
IsDigitsOnly Avg: 430963
Regex Avg: 464657,79

TryParse Min: 162742
IsDigitsOnly Min: 335646
Regex Min: 452121


For float :

TryParse Max : 3151995
IsDigitsOnly Max: 1392740
Regex Max : 1283451

TryParse Avg: 1391636
IsDigitsOnly Avg: 824029
Regex Avg: 501176

TryParse Min: 1187410
IsDigitsOnly Min: 706646
Regex Min: 476204

代码为long:

using System.Diagnostics;
using System.Text.RegularExpressions;

class Program
{
    private static Regex regex = new Regex("^[0-9]+$", RegexOptions.Compiled);

    static void Main(string[] args)
    {
        Stopwatch watch = new Stopwatch();
        watch.Start();
        watch.Stop();
        watch.Reset();
        List<TimeSpan> tryparse = new List<TimeSpan>();
        List<TimeSpan> isdigitsonly = new List<TimeSpan>();
        List<TimeSpan> regexss = new List<TimeSpan>();

        for (int say = 0; say < 1000; say++)
        { 
            float value;

            string test = Random.Shared.NextInt64(1000,long.MaxValue).ToString();
            watch.Start();
            for (int i = 0; i < 1000000; i++)
            {
                float.TryParse(test, out value);
            }
            watch.Stop();
            //Console.WriteLine("TryParse: " + watch.Elapsed);
            tryparse.Add(watch.Elapsed);

            watch.Reset();
            watch.Start();
            for (int i = 0; i < 1000000; i++)
            {
                IsDigitsOnly(test);
            }
            watch.Stop();
            //Console.WriteLine("IsDigitsOnly: " + watch.Elapsed);
            isdigitsonly.Add(watch.Elapsed);
            watch.Reset();
            watch.Start();
            for (int i = 0; i < 1000000; i++)
            {
                regex.IsMatch(test);
            }
            watch.Stop();
            regexss.Add(watch.Elapsed);
            watch.Reset();
            //   Console.WriteLine("Regex: " + watch.Elapsed);
     
            Console.Write("---------------------% " + (Convert.ToDecimal( say)/ 999 * 100).ToString("N2") + "---------------------------");
            Console.CursorLeft = 0;
        }
        Console.WriteLine();
        Console.WriteLine($"TryParse: {tryparse.Max(t => t.Ticks)}");
        Console.WriteLine($"IsDigitsOnly: {isdigitsonly.Max(t => t.Ticks)}");
        Console.WriteLine($"Regex: {regexss.Max(t => t.Ticks)}");
        Console.WriteLine();

        Console.WriteLine($"TryParse Avg: {tryparse.Average(t => t.Ticks)}");
        Console.WriteLine($"IsDigitsOnly Avg: {isdigitsonly.Average(t => t.Ticks)}");
        Console.WriteLine($"Regex Avg: {regexss.Average(t => t.Ticks)}");
        Console.WriteLine();
        Console.WriteLine($"TryParse Min: {tryparse.Min(t => t.Ticks)}");
        Console.WriteLine($"IsDigitsOnly Min: {isdigitsonly.Min(t => t.Ticks)}");
        Console.WriteLine($"Regex Min: {regexss.Min(t => t.Ticks)}");
        Console.ReadLine();
    }

    static bool IsDigitsOnly(string str)
    {
        foreach (char c in str)
        {
            if (c < '0' || c > '9')
                return false;
        }

        return true;
    }
}

我喜欢Linq，让它在第一次不匹配时退出，你可以这样做

string str = '0129834X33';
bool isAllDigits = !str.Any( ch=> ch < '0' || ch > '9' );

这很好，还有很多其他的方法，但这个也行

bool IsDigitsOnly(string str)
    {
        if (str.Length > 0)//if contains characters
        {
            foreach (char c in str)//assign character to c
            {
                if (c < '0' || c > '9')//check if its outside digit range
                    return false;
            }
        }else//empty string
        {
            return false;//empty string 
        }

        return true;//only digits
    }

您可以尝试使用正则表达式，通过使用c#中的. ismatch(字符串输入，字符串模式)方法测试输入字符串是否只有数字(0-9)。

using System;
using System.Text.RegularExpression;

public namespace MyNS
{
    public class MyClass
    {
        public void static Main(string[] args)
        {
             string input = Console.ReadLine();
             bool containsNumber = ContainsOnlyDigits(input);
        }

        private bool ContainOnlyDigits (string input)
        {
            bool containsNumbers = true;
            if (!Regex.IsMatch(input, @"/d"))
            {
                containsNumbers = false;
            }
            return containsNumbers;
        }
    }
}

问候

试试下面的代码:

bool isDigitsOnly(string str)
{
   try
   {
      int number = Convert.ToInt32(str);
      return true;
   }
   catch (Exception)
   {
      return false;
   }
}

public bool CheckforDigits(string x)
{    
    int tr;  
    return x.All(r=> int.TryParse(r.ToString(), out tr));
}