c# - DataGridView 单元格颜色变化

Question

我有一个测试程序，它构建一个数据表(26 行 x 6 列)作为 DataGridView 的数据源。
可以通过选择单元格并从 3 个 NumUpDown 控件之一输入值来编辑数据网格。
每个控件都有特定的颜色。为了保留信息，我将表格保存在用户设置中。
我将每个单元格的颜色信息保存在额外的表格单元格中。
问题:当我显示数据网格时，它从表中读取的值正常，但不显示应该根据额外单元格信息以编程方式添加的单元格颜色。
(我可以在诊断中看到单元格获得了正确的颜色，但它没有显示在数据网格中。
看起来 datagird 有一些颜色覆盖(？)。
附件是完整的工作代码。
在代码中查看更多信息。
任何人都可以运行它并找出为什么数据网格中没有显示颜色吗？谢谢。

using System;
using System.Data;
using System.Drawing;
using System.Web.UI.WebControls;
using System.Windows.Forms;

//This is a test program to do the following:
//1. Build an empty data table of 26 rows by 6 columns.
//2. The Table is bind (as DataSource) to a DataGridView.
//3. The DataGrid Colomns 0-3 can be filled with decimals by one of 3 NumericUpDown  controls.
//3. For each cell in cols 0-2 there is one in cols 3-5 that holds info which NumUpDn  was used.
//4. Each NumUpDn has specific color. The corresponding cells have the same backcolor.
//5. When the program starts, it builds the table from the Settings, and displays the  table in the datagrid.
//6. The cells in cols 0-2 are supposed to get the colors ad indicated in cols 3-5, but   they do not.
//To run, make a WinForm with a datagrid 'fareGrid' and 3 NumUpDn controls with background colors.  


namespace DataGridViewTest
{
public partial class Form1 : Form
{
    DataTable fareTable = new DataTable();

    int rowIndex;
    int colIndex;

    public Form1()
    {
        InitializeComponent();
        buildFareTable("fareTable");
        // Load the table (if exists)
        if (Properties.Settings.Default.fareTable != null)
            fareTable = Properties.Settings.Default.fareTable;
        paintFareTableCells(fareTable);

    }

    //Build the initial data table of 26R X 6C
    //Columns 3-5 are used to hold the color information of cols 0-2
    public void buildFareTable(string fareTableName)
    {
        fareTable.TableName = fareTableName;
        fareTable.Columns.Add("Weekday", typeof(Decimal));
        fareTable.Columns.Add("HalfDay", typeof(Decimal));
        fareTable.Columns.Add("Weekend", typeof(Decimal));

        //Adding 3 indexing columns that will hold the tables cell group
        fareTable.Columns.Add("IWeekday", typeof(String));
        fareTable.Columns.Add("IHalfDay", typeof(String));
        fareTable.Columns.Add("Iweekend", typeof(String));

        for (rowIndex = 0; rowIndex < 26; rowIndex++)
        {
            fareTable.Rows.Add();
        }
    }

    public void paintFareTableCells(DataTable fareTable)
    {
        fareDataGrid.DataSource = fareTable;

        for (rowIndex = 0; rowIndex < 26; rowIndex++)
        {
            for (colIndex = 0; colIndex < 3; colIndex++)
            {
                switch (fareTable.Rows[rowIndex][colIndex + 3].ToString())   //Check the color index columns 3-5
                {
                    case "low": fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Green;  
                        break;
                    case "med": fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Yellow; 
                        break;
                    case "high": fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Red;  
                        break;
                    default:
                        break;
                }

                // Diagnostics: Check cell's color. At this point, Colors are OK!  
                Color color = fareDataGrid[colIndex, rowIndex].Style.BackColor;  
            }
        }
    }

   //Update the cells by 3 NumUpDn controls.
    private void numericUpDownFareHigh_ValueChanged(object sender, EventArgs e)
    {
        editFareTableCells(sender);
    }
    private void numericUpDownFareMed_ValueChanged(object sender, EventArgs e)
    {
        editFareTableCells(sender);
    }

    private void numericUpDownFareLow_ValueChanged(object sender, EventArgs e)
    {
        editFareTableCells(sender);
    }

    public void editFareTableCells(Object sender)
    {
        foreach (DataGridViewCell cell in fareDataGrid.SelectedCells)
        {
            if (cell.ColumnIndex < 3)
            {
                cell.Value = ((NumericUpDown)sender).Value;
                cell.Style.BackColor = ((NumericUpDown)sender).BackColor;
                fareDataGrid[cell.ColumnIndex + 3, cell.RowIndex].Value = ((NumericUpDown)sender).Tag;   //Uses cols 3-5 to hold cost level info.
            }
        }
    }

    //Use settings to preserve the data
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        Properties.Settings.Default.fareTable = this.fareTable;
        Properties.Settings.Default.Save();
    }
}
}

Answer 1

变色代码必须在事件处理程序中；具体来说，DataBindingComplete 事件处理程序。我按如下方式重写了您的代码:

public void paintFareTableCells(DataTable fareTable)
{
    fareDataGrid.DataSource = fareTable;
}

void fareDataGrid_DataBindingComplete(object sender, DataGridViewBindingCompleteEventArgs e)
{
    for (rowIndex = 0; rowIndex < 26; rowIndex++)
    {
        for (colIndex = 0; colIndex < 3; colIndex++)
        {
            switch (fareTable.Rows[rowIndex][colIndex + 3].ToString())   //Check the color index columns 3-5
            {
                case "low":
                    fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Green;
                    break;
                case "med":
                    fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Yellow;
                    break;
                case "high":
                    fareDataGrid[colIndex, rowIndex].Style.BackColor = Color.Red;
                    break;
                default:
                    break;
            }

            // Diagnostics: Check cell's color. At this point, Colors are OK!  
            Color color = fareDataGrid[colIndex, rowIndex].Style.BackColor;
        }
    }
}

单元格现在根据需要更改颜色。

顺便说一句，不要忘记在构造函数中订阅事件处理程序:

fareDataGrid.DataBindingComplete += new DataGridViewBindingCompleteEventHandler(fareDataGrid_DataBindingComplete);