To split string array and return as a string

You can try something like below here op1 and op2 strings will hold your output and have it updated as per your need.

string sss;
string[] ss = { "1||age--11||gender--Female|||||", "0||age--16||gender--Male|||||" };

string op1 = String.Empty;
string op2 = String.Empty;

for (int i = 0; i < ss.Length; i++)
{
     sss = ss[i].ToString().Replace("||",",").Replace(",,","");
     string[] p = sss.Split(',');
     op1 += String.Format("{0},", p[1]);//age details
     op2 += String.Format("{0},", p[2]);//gentder details
}

I can't see any reason why you are using Replace on commas as there are no commas in your input string - the comma that appears is the array separator. The assignment to string[] ss is essentially the same as

ss[0] = "1||age--11||gender--Female|||||";
ss[1] = "0||age--16||gender--Male|||||" ;

You can Split each entry on the array on the vertical bar |. If you are sure that every item in the array will be in that same format then you could use the StringSplitOptions.RemoveEmptyEntries option.

If you are going to reconstruct a string from these items then you should use the StringBuilder[^] class

The code below assumes that each of the items in the array ss is in exactly the same format as shown in your question

string[] ss = { "1||age--11||gender--Female|||||", "0||age--16||gender--Male|||||" };

StringBuilder sb1 = new StringBuilder("(");
StringBuilder sb2 = new StringBuilder("(");
for (int i = 0; i < ss.Length; i++)
{
    var s1 = ss[i].Split(new []{'|'}, StringSplitOptions.RemoveEmptyEntries);
    sb1.Append(s1[1]);
    if(i < ss.Length - 1) sb1.Append(",");
    sb2.Append(s1[2]);
    if (i < ss.Length - 1) sb2.Append(",");
}
sb1.Append(")");
sb2.Append(")");
            
Debug.Print(sb1.ToString());
Debug.Print(sb2.ToString());

Alternatively you can search for the item that begins with "age", "gender" - example:

foreach (var s in s1.Where(s => s.StartsWith("age")))
{
    sb1.Append(s);
    if (i < ss.Length - 1) sb1.Append(",");
}