Code :
string[] X = Regex.Split(X, ",");
string[] A = Regex.Split(A, ",");
string[] B = Regex.Split(B, ",");
string[] C= Regex.Split(C, ",");
string[] D = Regex.Split(D, ",");
for (int i = 0; i < splitfirsts.Length; i++)
{
Console.WriteLine("{0}{1}{2}{3}{4}",
X[i], A[i], B[i], C[i], D[i]);
}
X = 1,2,3
A = 4,5,6
B = 7,8,9
C = Adam,Mark,Tom
D = 16,21,88
147Adam16
258Mark21
369Tom88
string newstring = 147Adam16258Mark21369Tom88
`string[] X = Regex.Split(X, ",");
string[] A = Regex.Split(A, ",");
string[] B = Regex.Split(B, ",");
string[] C= Regex.Split(C, ",");
string[] D = Regex.Split(D, ",");
StringBuilder sb = new StringBuilder();
for (int i = 0; i < splitfirsts.Length; i++)
{
sb.AppendFormat("{0}{1}{2}{3}{4}",
X[i], A[i], B[i], C[i], D[i]);
}
Console.WriteLine(sb.ToString());`
Do mark as answer if it helps.