there's an error in this codes, can you help me fo fix it

Answer 1

First there have to be copied l characrers. Second if starts with i = 30 then cannot come into the loop if a input string will be shorter then 30 etc. Right code as follows:
i=0;
while(i<l) {
string tmp=str1[i].ToString();
str2[i] = tmp;
i++;
}

Answer 2

string str1;
int i,l;

Console.Write("Input the string : This is a string to be copied ");

str1 = Console.ReadLine();
l=str1.Length;
string[] str2=new string[l];

i=30;
while(i<l) { string tmp=str1[i].ToString();

str2[i] = tmp;
i++;

} Console.Write("\nThe First string is : {0}\n", str1 );
Console.Write("The Second string is : {0}\n", string.Join("",str2));
Console.Write("Number of characters copied : {0}\n\n", ++i);