Define variable inside a for(I ..) loop

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hi
how should i do this work?

C#

string s1;
string s2;
string s3;

i want to define variable inside of loop:

C#

for (i=1;i=3;i++)
{
   string s+i.tostring();
}

but s+i.tostring() is wrong.

thanks

What I have tried:

i don't know what should i do

help

Posted 19-Feb-19 3:58am

Member 13522501

Updated 19-Feb-19 20:15pm

Maciej Los

v2

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3 solutions

Solution 1

It goes like this:

for (var i = 1; i <= 3; i++)
{
    var myString = "s" + i;
}

Posted 19-Feb-19 4:13am

TheRealSteveJudge

Solution 2

TheRealSteveJudge is right, but ... the whole loop is pointless as shown as the variable will go out of scope at the end of the loop and will be thrown away.

A better solution would be this:

C#

string s = "";
for (int i = 1; i <= 3; i++)
   {
   s = s + i.ToString();
   }
Console.WriteLine(s);

Or for larger loops:

C#

StringBuilder sb = "";
for (int i = 1; i <= 3; i++)
   {
   sb.Append(i.ToString());
   }
Console.WriteLine(sb.ToString());

As strings are immutable - when you concatenate strings you create a new string and have to copy all the info across - it can get incredibly inefficient in terms of processor power and memory if you aren't careful. The StringBuilder class reduces that to a minimum by being an expandable string.

Posted 19-Feb-19 4:44am

OriginalGriff

Updated 19-Feb-19 5:03am

v2

Comments

TheRealSteveJudge 20-Feb-19 2:45am

You're right with

the variable will go out of scope

But it is nearly impossible to provide a perfect answer to such a poor question.
The StringBuilder hint is valuable though. 5*

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Dave Kreskowiak · Accepted Answer · 2019-02-19T04:58:00

If you're trying to define some string variables named s1, s2, and s3, that's not going to work. You cannot define variable names like that at runtime.

You can define a collection that will hold strings, for example:

C#

List<string> myStrings = new List<string>();
myStrings.Add("some string content");

or an array of strings:

C#

string[] myStrings = new string[3];
myStrings[0] = "some string content";

There's variety of ways of holding a collection of items. You don't normally define a single variable for each item.