Do You Have a Case of var Guilt

do-you-have-a-case-of-var-guilt-1.cs

public string reverse(string toReverse)
{
    var reversed = "";
    var lastCharacterIndex = toReverse.Length -1;
    var firstCharacterIndex = 0;
    for(var index = lastCharacterIndex; index >= firstCharacterIndex; index--)
    {
        var letter = toReverse[index];
        reversed += letter;
    }
 
    return reversed;
}