c# - Merge two strings

Note that this is not concatenating two strings

try
{

   Console.WriteLine("Please enter the first string.");

   string sFirstString = Console.ReadLine().Trim();

   Console.WriteLine();

   Console.WriteLine("Please enter the second string.");

   string sSecondString = Console.ReadLine().Trim();

   Console.WriteLine();

   if (string.IsNullOrEmpty(sFirstString) && !string.IsNullOrEmpty(sSecondString))

   {

       Console.WriteLine("The strings after merging");

       Console.WriteLine(sSecondString);

   }

   else if (!string.IsNullOrEmpty(sFirstString) && string.IsNullOrEmpty(sSecondString))

   {

       Console.WriteLine("The strings after merging");

       Console.WriteLine(sFirstString);

   }

   else if (!(string.IsNullOrEmpty(sFirstString) || string.IsNullOrEmpty(sSecondString)))

   {

       char[] caFirstString = sFirstString.ToCharArray();

       char[] caSecondString = sSecondString.ToCharArray();

       StringBuilder oMergedString = new StringBuilder();

       for (int iIndex = 0; iIndex < (sFirstString.Length >= sSecondString.Length ? sFirstString.Length : sSecondString.Length); iIndex++)

       {

            if (iIndex < (sFirstString.Length >= sSecondString.Length ? sSecondString.Length : sFirstString.Length))

            {

                 oMergedString.Append(caFirstString[iIndex]);

                 oMergedString.Append(caSecondString[iIndex]);

            }

            else if (iIndex < sFirstString.Length)

                 oMergedString.Append(caFirstString[iIndex]);

            else

                 oMergedString.Append(caSecondString[iIndex]);

       }

       Console.WriteLine(oMergedString.ToString());

    }

    else

       Console.WriteLine("The strings cannot be empty.");

}
catch(Exception ex)
{
          Console.WriteLine(ex.Message);
}


Output