在何处以及如何使用&&运算符

Question

I have this piece of code which i simplified from my app. It does what I want but I know its not put in the most efficient way because I'm still having some trouble understanding the && and & operators.

if (AgeInput.Text.Equals(""))
{
    Textblock1.Text = "✘";
}
else if (AgeInput.Text.All(Char.IsNumber)){
    Textblock1.Text = "✔";
    //DO-THIS-A
}
else
{
    Textblock1.Text = "✘";
}

I need it to make sure there is no white spaces in the string and to also check so its not empty and finally check if its a number, If it ticks all those requirements it will //DO-THIS-A

Whats the most efficient way to do this?

EDIT: If somebody knows how to make a XAML textbox numerical only (so no whitespaces) that would be even better (only a single property or don't worry otherwise)

Answer 1

if(!String.IsNullOrEmpty(AgeInput.Text) && AgeInput.Text.All(char.IsNumber))
    Textblock1.Text = "✔";
else
    Textblock1.Text = "✘";

String.IsNullOrEmpty returns true if the input is as stated: Null or Empty.

We Invert that with the " ! ", so that it returns true if it isn't empty.

Then we add the && Operator to expand the if condition and ask if the text only contains numbers.

Also look here: For a description of the difference between &, && and |, ||

Answer 2

Not really sure I understand your question, because && and & are for totally different uses.

if (string.IsNullOrWhiteSpace(AgeInput.Text))
{
    Textblock1.Text = "✘";
}
else if(Char.IsNumber(AgeInput.Text.All))
{
    Textblock1.Text = "✔";
}

The & is a binary operator and && is a logical operator.