C # 测试一个字符串是否是一个整数？

Use the int.TryParse method.

string x = "42";
if(int.TryParse(x, out int value))
// Do something

If it successfully parses it will return true, and the out result will have its value as an integer.

If you just want to check type of passed variable, you could probably use:

    var a = 2;
if (a is int)
{
//is integer
}
//or:
if (a.GetType() == typeof(int))
{
//is integer
}

I think that I remember looking at a performance comparison between int.TryParse and int.Parse Regex and char.IsNumber and char.IsNumber was fastest. At any rate, whatever the performance, here's one more way to do it.

        bool isNumeric = true;
foreach (char c in "12345")
{
if (!Char.IsNumber(c))
{
isNumeric = false;
break;
}
}

I've been coding for about 2 weeks and created a simple logic to validate an integer has been accepted.

    Console.WriteLine("How many numbers do you want to enter?"); // request a number
string input = Console.ReadLine(); // set the input as a string variable
int numberTotal; // declare an int variable


if (!int.TryParse(input, out numberTotal)) // process if input was an invalid number
{
while (numberTotal  < 1) // numberTotal is set to 0 by default if no number is entered
{
Console.WriteLine(input + " is an invalid number."); // error message
int.TryParse(Console.ReadLine(), out numberTotal); // allows the user to input another value
}


} // this loop will repeat until numberTotal has an int set to 1 or above

you could also use the above in a FOR loop if you prefer by not declaring an action as the third parameter of the loop, such as

    Console.WriteLine("How many numbers do you want to enter?");
string input2 = Console.ReadLine();


if (!int.TryParse(input2, out numberTotal2))
{
for (int numberTotal2 = 0; numberTotal2 < 1;)
{
Console.WriteLine(input2 + " is an invalid number.");
int.TryParse(Console.ReadLine(), out numberTotal2);
}


}

if you don't want a loop, simply remove the entire loop brace

This function will tell you if your string contains ONLY the characters 0123456789.

private bool IsInt(string sVal)
{
foreach (char c in sVal)
{
int iN = (int)c;
if ((iN > 57) || (iN < 48))
return false;
}
return true;
}

This is different from int.TryParse() which will tell you if your string COULD BE an integer.
eg. " 123\r\n" will return TRUE from int.TryParse() but FALSE from the above function.

...Just depends on the question you need to answer.

its simple... use this piece of code

bool anyname = your_string_Name.All(char.IsDigit);

it will return true if your string have integer other wise false...

For Wil P solution (see above) you can also use LINQ.

var x = "12345";
var isNumeric = !string.IsNullOrEmpty(x) && x.All(Char.IsDigit);

private bool isNumber(object p_Value)
{
try
{
if (int.Parse(p_Value.ToString()).GetType().Equals(typeof(int)))
return true;
else
return false;
}
catch (Exception ex)
{
return false;
}
}

Something I wrote a while back. Some good examples above but just my 2 cents worth.

If you only want to check whether it's a string or not, you can place the "out int" keywords directly inside a method call. According to dotnetperls.com website, older versions of C# do not allow this syntax. By doing this, you can reduce the line count of the program.

string x = "text or int";
if (int.TryParse(x, out int output))
{
// Console.WriteLine(x);
// x is an int
// Do something
}
else
{
// x is not an int
}

If you also want to get the int values, you can write like this.

Method 1

string x = "text or int";
int value = 0;
if(int.TryParse(x, out value))
{
// x is an int
// Do something
}
else
{
// x is not an int
}

Method 2

string x = "text or int";
int num = Convert.ToInt32(x);
Console.WriteLine(num);

Referece: https://www.dotnetperls.com/parse

Maybe this can be another solution

try
{
Console.Write("write your number : ");
Console.WriteLine("Your number is : " + int.Parse(Console.ReadLine()));
}
catch (Exception x)
{
Console.WriteLine(x.Message);
}
Console.ReadLine();