C. Design a calculator to determine whether the input is a number

Determine if it's a number.

String. private bool isnumeric(string str)if (str == null ||== 0)return false;

ascii = new ;

byte bytestr = ;

foreach(byte c in bytestr)if (c < 48 ||c > 57)

return false;

return true;

public bool isnumericregex(string str)

reg = new

return ;

Add a judgment to the button1 click event and you're good to go.

if("Entered",out output int)) textbox += output.

If you enter a number other than a number, it will return false

It's as simple as that, it doesn't have to be that complicated.

Create a stack, put strings in it, then take it out (pop), and use it in turn to determine whether it is a number or not, and if there is a non-match, you will know that it is not a number.

The idea I said is so detailed, you just follow it, it's very simple. If you don't understand something, you can check MSDN, so that you can learn something, and it is not possible to have everything ready-made.

Since you are a beginner, you should know that MSDN is a must-have, and almost all questions (which beginners don't understand) can find answers there.

private void button1_click(object sender, eventargs e)

Else you can see it.

My personal recommendation is to use regular expressions to judge the best.

The regular expression for judging real numbers is -d+d*$ specific method.

1. Add a reference.

using ;

2、string regex = @"^-?d+\.d*$";

bool result = character, regex);

result: If the result is true, the character is a real number.

Heh, regular expressions.

Custom judgments.

Spatial judgment. Write whatever you want.

No need to write** VS2005 There is a control to determine whether it is a number comparevalidator should be this to set its properties.

Write a method, and write this paragraph in the method**:

public bool isnumber(string str)

return true;

Pull two textbox controls as numeric inputs; Pull a few button controls, click the controls to perform addition, subtraction, multiplication and division operations.

Previously written, can meet the idea of lz da ze

Static void main (string args) is a prime number. ", num);

else is not a prime number. ", num);}

label can only be assigned to it programmatically, not by the user.

You can take out the string entered by the user one at a time, and then judge whether it belongs to 0-9, if not, it will prove that it is not a number, I just give the principle, **You can write it yourself.

regularexpressionvalidator

This control can be verified.

Then write an expression and that's it.

It can be directly bound to a backend property.

Or enter the event with the keyboard.

You can use regular expressions, too.