Looping Between Grid view rows and columns

Check the below code, this may help you

string[] arrayString = new string[] { "A", "B", "C", "D" };
for (int i = 0; i < arrayString.Length; i++)
{
int nxtIndex = i + 1;
if (i == arrayString.Length - 1)
nxtIndex = i - (arrayString.Length - 1);
Console.WriteLine(arrayString[i] + arrayString[nxtIndex]);
}
for (int i = 0; i < arrayString.Length; i++)
{
string strValue = "";
for (int j = 0; j < arrayString.Length; j++)
{
if (i != j)
strValue += string.IsNullOrEmpty(strValue) ? arrayString[i] + arrayString[j] : "," + arrayString[i] + arrayString[j];
}
Console.WriteLine(strValue);
}