if (dataGridView1.SelectedRows.Count > 0)
            {
                DialogResult result = MessageBox.Show("确定要删除选中项吗？", "提示", MessageBoxButtons.OKCancel, MessageBoxIcon.Information);
                if (result == DialogResult.OK)
                {
                    for (int i = dataGridView1.SelectedRows.Count; i >= 1; i--)//从下往上删
                    {
                        dataGridView1.Rows.RemoveAt(dataGridView1.SelectedRows[i - 1].Index);
                    }
                    if (radioButton1.Checked == true) 
                    {
                        SqlCommandBuilder scb = new SqlCommandBuilder(sa);
                        sa.Update(ds.Tables["DATAWEI"]);
                    }
                    else if (radioButton2.Checked == true)
                    {
                        SqlCommandBuilder scb = new SqlCommandBuilder(sa);
                        sa.Update(ds.Tables["MAINDATAWEI"]);
                    }
                    else 
                    {
                        SqlCommandBuilder scb = new SqlCommandBuilder(sa);
                        sa.Update(ds.Tables["OLDDATAWEI"]);
                    }
                    
                }
            }

            for (int i = dataGridView1.Rows.Count - 1; i >= 0; i--)
            {
                if (dataGridView1.Rows[i].Selected)
                {
                    //删除
                }
            }

------解决方案--------------------
写在一个rowcommand 事件里面好像可以

------解决方案--------------------
 for (int i = dataGridView1.SelectedRows.Count; i >= 1; i--)//从下往上删
                   {
                       dataGridView1.Rows.RemoveAt(dataGridView1.SelectedRows[i - 1].Index);
                   }


你删了一个后，选中的数就少一个，，你这样写是不规范的