How to create dynamic incrementing variable using “for” loop in C#

You can't create dynamically-named variables. All you can do - it to create some collection or array, and operate with it. I think the best class for you is generic List<>:

List<String> listWithDynamic = new List<String>();
for (int i = 1; i < limit; i +=1)
{
    listWithDynamic.Add(string.Format("track_{0}", i));
    ...
}

Assuming you want strings:

for (int i = 1; i < limit; i +=1)
{
    string track = string.Format("track_{0}", i);
    ...
}

But when you already have variables called track_1, track_2, track_3, track_4 you will need an array or List:

var tracks = new TrackType[] { track_1, track_2, track_3, track_4 } ;

for (int i = 0; i < tracks.length; i++)
{
    var track = tracks[i];  // tracks[0] == track_1
    ...
}

Obvious Solution

for (var i = 0; i < 10; i++)
{
    var track = string.Format("track_{0}", i);

}

Linq-Based Solution

foreach (var track in Enumerable.Range(0, 100).Select(x => string.Format("track_{0}", x)))
{

}

Operator-Based Solution This is somewhat hacky, but fun none-the-less.

for (var i = new Frob(0, "track_{0}"); i < 100; i++)
{
    Console.WriteLine(i.ValueDescription);
}

struct Frob
{
    public int Value { get; private set; }
    public string ValueDescription { get; private set; }
    private string _format;

    public Frob(int value, string format)
        : this()
    {
        Value = value;
        ValueDescription = string.Format(format, value);
        _format = format;
    }

    public static Frob operator ++(Frob value)
    {
        return new Frob(value.Value + 1, value._format);
    }

    public static Frob operator --(Frob value)
    {
        return new Frob(value.Value - 1, value._format);
    }

    public static implicit operator int(Frob value)
    {
        return value.Value;
    }

    public static implicit operator string(Frob value)
    {
        return value.ValueDescription;
    }

    public override bool Equals(object obj)
    {
        if (obj is Frob)
        {
            return ((Frob)obj).Value == Value;
        }
        else if (obj is string)
        {
            return ((string)obj) == ValueDescription;
        }
        else if (obj is int)
        {
            return ((int)obj) == Value;
        }
        else
        {
            return base.Equals(obj);
        }
    }

    public override int GetHashCode()
    {
        return Value;
    }

    public override string ToString()
    {
        return ValueDescription;
    }
}

don't know if I get your question, but I will try:

for(var i = 1; i < yourExclusiveUpperbound; i++)
{
   var track = String.Format("$track_{0}", i);
   // use track
}

or with some LINQ-Magic:

foreach(var track in Enumerate.Range(1, count)
                              .Select(i => String.Format("$track_{0}", i)))
{
   // use track
}

Do as follow:

for (int i = 0; i < lenght; i ++)
{
    any work do in loop
}

No, we can't create dynamically named variables in a loop. But, there are other elegant ways to address the problem instead of creating dynamically named variables.

One could be, create an array or list before the loop and store values in array / list items in the loop. You can access the array / list later anywhere in your code. If you know which variable you want to use (track_1, track_2, ...), you can simply access it from the array / list (tracks[1], tracks[2], ...).

List<String> tracks = new List<String>();
for (int i = 1; i < limit; i++)
{
    Track track = new Track();
    tracks.Add(track);
    ...
}

  for (int i=5;i<30;(i%2==0)?i=i+4:i=i+2) {
     cout<<i;
     cout<<endl;
   }

Using ternary operator can help.