保存前，把空值改为零，然后保存

for (int i = 0; i < this.dataGridView_gzd_save.Rows.Count; i++)

            {
for (int j = 0; j < this.dataGridView_gzd_save.Columns.Count; j++)
                {
if (this.dataGridView_gzd_save.Rows[i].Cells[j].Value == "" || this.dataGridView_gzd_save.Rows[i].Cells[j].Value == null)
{
this.dataGridView_gzd_save.Rows[i].Cells[j].Value = "0";
}
                }
            }