Variables retain their value in a loop?-CodePudding

If I run this simple code in a console app:

For i As Integer = 1 To 10
    Dim s As String = i.ToString()
    Dim x As Decimal
    If i = 1 Then
        x = Decimal.Parse(s)
    End If
    Console.WriteLine(x.ToString())
Next
Console.ReadLine()

Unexpectedly, x retains its value of 1 and so 1 gets printed 10 times. I thought each iteration of the loop was its own code block, and that the state didn't carry over? Why does this happen? I would expect x to have the default value of System.Decimal.

Same thing happens in C#, except that the complier won't let you call ToString() on an uninitialized variable, but if you set a breakpoint in Visual Studio, you can see that x retains its value of 1.

for (int i = 1; i <= 10; i  )
{
    string s = i.ToString();
    Decimal x;
    if(i == 1)
    {
        x = Decimal.Parse(s);
    }
    // Value of x remains 1
}
Console.ReadLine();

CodePudding user response：

thought each iteration of the loop was its own code block, and that the state didn't carry over

It does "carry over."

int i is scoped to the entire range of the loop, with values from 1 to 10.

The if statement only executes on the first iteration, and x is scoped as a local variable to the outer method (assuming the loop is entered), not only the loop body. That being said, after & outside the loop, x == 1 as well.

In fact, Decimal x; in the loop is redundant, and you have the same execution logic as

string s;
Decimal x;
for (int i = 1; i <= 10; i  )
{
    s = i.ToString();

    if(i == 1)
    {
        x = Decimal.Parse(s);
    }
    Console.WriteLine(x);
}
// x still defined here

CodePudding user response：

To make some sense of what you want, it should be just like this:

For i As Integer = 1 To 10
    If i = 1 Then
      Console.WriteLine(Decimal.Parse(i.ToString()))
    End If
Next

This will give you the same result you want but it is readable.