простой способ таков:
var parameters = new string[ids.Length];
var cmd = new SqlCommand();
for (int i = 0; i < ids.Length; i++)
{
parameters[i] = string.Format("@Id{0}", i);
cmd.Parameters.AddWithValue(parameters[i], ids[i]);
}
cmd.CommandText = string.Format("update table set col = 'something' where id in ({0})", string.Join(", ", parameters));