dataGridView中两列的值比较大小

Question

 
               
                   for (int i = 0; i < dataGridView1.Rows.Count; i++)
                   {                       if (Convert.ToInt32(dataGridView1.Rows[i].Cells[4].Value.ToString()) > Convert.ToInt32(dataGridView1.Rows[i].Cells[3].Value.ToString()))
                        {
                           dataGridView1.Rows[i].ErrorText = "实际入库量不能大于订购量";
                           MessageBox.Show("实际入库量不能大于订购量");
                            e.Cancel = true;
                        }
                   }我想比较3、4列两个单元的值，但这样写不行，说什么对象没初始化，请问该怎么改或者有什么更好的方法实现，O(∩_∩)O谢谢！！
                

Answer 1

string s1 = dataGridView1.Rows[i].Cells[4].Value.ToString();
string s2 = dataGridView1.Rows[i].Cells[3].Value.ToString();
如果是数值型的,最好转成数值再比较,比较真实,字符串的大小比较有时候可能结果不是
你想要的,
decimal d1 = (decimal)dataGridView1.Rows[i].Cells[4].Value.ToString();
decimal d2 = (decimal)dataGridView1.Rows[i].Cells[3].Value.ToString();对象没有初始化,有可能是在你写的代码的事件加载时,dataGridView1尚没有数据.

Answer 2

在转换前你得确认 获取的值是不是为空啊，然后再进行转换，不然会出错下面这样就是转换失败的时候值为0double d1=0.0;
double.TryParse(dataGridView1.Rows[i].Cells[4].Value.ToString(),out d1);

Answer 3

总结：
先dataGridView1.Rows[i].Cells[n].Value判断是否为空
然后数据类型转换
然后再比较

Answer 4

你的事件应该是写在Validated 或Validating 中的吧,应该先用e.fomattedvalue.tostring.trim判断单元格是否为空(包含null和空格),当不为null或空的时候再用你的代码进行比较.因为dgv单元格在没赋值的时候取出来的值是nothing(null)

Answer 5

第四列的数据时通过键盘输入的，然后与第三列比较，我是这样写的，但发现第4列还是不能实例化 private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            bool flag = false;
            if (e.ColumnIndex == 4)
            {
                try
                {
                    if (!String.IsNullOrEmpty(e.FormattedValue.ToString()))
                    {
                        flag = true;
                        decimal val = decimal.Parse(e.FormattedValue.ToString());                    }
                }
                catch (Exception ex)
                {
                    flag = false;
                    dataGridView1.Rows[e.RowIndex].ErrorText = "必须输入数字";
                    MessageBox.Show("必须输入数字");
                    e.Cancel = true;                }
            
                if (flag&&e.FormattedValue.ToString().Trim()!=null)
                {
                                       for (int i = 0; i < dataGridView1.Rows.Count; i++)
                    {
                        decimal d1 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[4].Value.ToString());
                        decimal d2 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[3].Value.ToString());
                        if (d1 > d2)
                        {
                            dataGridView1.Rows[i].ErrorText = "实际入库量不能大于订购量";
                            MessageBox.Show("实际入库量不能大于订购量");
                            e.Cancel = true;
                        }
                    }
                }            }
        }        private void btncheck_Click(object sender, EventArgs e)
        {
             groushowen.Location = new System.Drawing.Point(groushowen.Location.X,groushowen.Location.Y);
             groushowen.Visible = true;
             string s = null;
             for (int i = 0; i < dataGridView1.Rows.Count; i++)
             {
                 s = dataGridView1.Rows[i].Cells[4].Value.ToString();
             }
             this.enterListTableAdapter.Fill(this.wgycDataSet3.EnterList, s);
        }

Answer 6

 
   第4列的数据是用键盘输入的，然后与第3列数据进行比较，下面是我自己写的，但发现还是会出现第四列对象没有初始化的问题，请问我该怎么改，或者有别的方法能实现吗？谢谢！！
private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            bool flag = false;
            if (e.ColumnIndex == 4)
            {
                try
                {
                    if (!String.IsNullOrEmpty(e.FormattedValue.ToString()))
                    {
                        flag = true;
                        decimal val = decimal.Parse(e.FormattedValue.ToString());                    }
                }
                catch (Exception ex)
                {
                    flag = false;
                    dataGridView1.Rows[e.RowIndex].ErrorText = "必须输入数字";
                    MessageBox.Show("必须输入数字");
                    e.Cancel = true;                }
            
                if (flag&&e.FormattedValue.ToString().Trim()!=null)
                {
                                       for (int i = 0; i < dataGridView1.Rows.Count; i++)
                    {
                        decimal d1 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[4].Value.ToString());
                        decimal d2 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[3].Value.ToString());
                        if (d1 > d2)
                        {
                            dataGridView1.Rows[i].ErrorText = "实际入库量不能大于订购量";
                            MessageBox.Show("实际入库量不能大于订购量");
                            e.Cancel = true;
                        }
                    }
                }            }
        }        private void btncheck_Click(object sender, EventArgs e)
        {
             groushowen.Location = new System.Drawing.Point(groushowen.Location.X,groushowen.Location.Y);
             groushowen.Visible = true;
             string s = null;
             for (int i = 0; i < dataGridView1.Rows.Count; i++)
             {
                 s = dataGridView1.Rows[i].Cells[4].Value.ToString();
             }
             this.enterListTableAdapter.Fill(this.wgycDataSet3.EnterList, s);
        }

Answer 7

 
   第4列的数据是用键盘输入的，然后与第3列数据进行比较，下面是我自己写的，但发现还是会出现第四列对象没有初始化的问题，请问我该怎么改，或者有别的方法能实现吗？谢谢！！
private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            bool flag = false;
            if (e.ColumnIndex == 4)
            {
                try
                {
                    if (!String.IsNullOrEmpty(e.FormattedValue.ToString()))
                    {
                        flag = true;
                        decimal val = decimal.Parse(e.FormattedValue.ToString());                    }
                }
                catch (Exception ex)
                {
                    flag = false;
                    dataGridView1.Rows[e.RowIndex].ErrorText = "必须输入数字";
                    MessageBox.Show("必须输入数字");
                    e.Cancel = true;                }
            
                if (flag&&e.FormattedValue.ToString().Trim()!=null)
                {
                                       for (int i = 0; i < dataGridView1.Rows.Count; i++)
                    {
                        decimal d1 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[4].Value.ToString());
                        decimal d2 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[3].Value.ToString());
                        if (d1 > d2)
                        {
                            dataGridView1.Rows[i].ErrorText = "实际入库量不能大于订购量";
                            MessageBox.Show("实际入库量不能大于订购量");
                            e.Cancel = true;
                        }
                    }
                }            }
        }        private void btncheck_Click(object sender, EventArgs e)
        {
             groushowen.Location = new System.Drawing.Point(groushowen.Location.X,groushowen.Location.Y);
             groushowen.Visible = true;
             string s = null;
             for (int i = 0; i < dataGridView1.Rows.Count; i++)
             {
                 s = dataGridView1.Rows[i].Cells[4].Value.ToString();
             }
             this.enterListTableAdapter.Fill(this.wgycDataSet3.EnterList, s);
        }

Answer 8

   第4列的数据是用键盘输入的，然后与第3列数据进行比较，下面是我自己写的，但发现还是会出现第四列对象没有初始化的问题，请问我该怎么改，或者有别的方法能实现吗？谢谢！！
private void dataGridView1_CellValidating(object sender, DataGridViewCellValidatingEventArgs e)
        {
            bool flag = false;
            if (e.ColumnIndex == 4)
            {
                try
                {
                    if (!String.IsNullOrEmpty(e.FormattedValue.ToString()))
                    {
                        flag = true;
                        decimal val = decimal.Parse(e.FormattedValue.ToString());                    }
                }
                catch (Exception ex)
                {
                    flag = false;
                    dataGridView1.Rows[e.RowIndex].ErrorText = "必须输入数字";
                    MessageBox.Show("必须输入数字");
                    e.Cancel = true;                }
            
                if (flag&&e.FormattedValue.ToString().Trim()!=null)
                {
                                       for (int i = 0; i < dataGridView1.Rows.Count; i++)
                    {
                        decimal d1 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[4].Value.ToString());
                        decimal d2 = Convert.ToDecimal(dataGridView1.Rows[i].Cells[3].Value.ToString());
                        if (d1 > d2)
                        {
                            dataGridView1.Rows[i].ErrorText = "实际入库量不能大于订购量";
                            MessageBox.Show("实际入库量不能大于订购量");
                            e.Cancel = true;
                        }
                    }
                }            }
        }        private void btncheck_Click(object sender, EventArgs e)
        {
             groushowen.Location = new System.Drawing.Point(groushowen.Location.X,groushowen.Location.Y);
             groushowen.Visible = true;
             string s = null;
             for (int i = 0; i < dataGridView1.Rows.Count; i++)
             {
                 s = dataGridView1.Rows[i].Cells[4].Value.ToString();
             }
             this.enterListTableAdapter.Fill(this.wgycDataSet3.EnterList, s);
        }