C# 源数组长度不足。请检查 srcIndex 和长度以及数组的下限。

string strConn = "Data Source=127.0.0.1;Initial Catalog=zy;User ID=sa;Password=229107my229107m";
SqlConnection ConnAcc = new SqlConnection(strConn);
string strSQL = "SELECT * FROM Group_SGK3 ";
SqlDataAdapter de = new SqlDataAdapter(strSQL, ConnMdb);
try
{
//da.Fill(dt);
dtData.Clear();
de.Fill(dtData);

}
catch
{
break;
}
for (int n = 0; n < 7; n++)
{
int GK;
foreach (DataRow rdr in dtData.Rows)
{

int SGK = Convert.ToInt32(rdr["SGK"]);
GK = SGK << n;


if (Convert.ToBoolean(rdr["state1"]))
{


byte[] gk = new byte[8];
Array.Copy(HexStrToHexBytes(GK.ToString()), 0, gk, 7, 1);
Array.Copy(HexStrToHexBytes(dr["pdk"].ToString()), 0, pdk, 7, 1);// pdk buf: 0,0,0,0,0,0,0,0xcd
;
SKeyValue = SKeyValue1;
byte[] EncryptSk = EncryptDES(SKeyValue, gk);


EDS[6] = 0x01;
Array.Copy(EncryptSk, 0, EDS, 7, EncryptSk.Length);
//Thread.Sleep(5);
}
else
{


请问： Array.Copy(HexStrToHexBytes(GK.ToString()), 0, gk, 7, 1);这行提示错误说“源数组长度不足。请检查 srcIndex 和长度以及数组的下限。”这是怎么回事呢？应该怎么改？请各位大师指点！