你应该通过 Style/Trigger 或 Binding 与转换器之类的

You should be doing this through Style/Trigger or Binding with a converter like

<DataGrid Name="dataGrid"
          ...>
    <DataGrid.Columns>
        <DataGridTextColumn Header="column4" Binding="{Binding column4}">
            <DataGridTextColumn.CellStyle>
                <Style TargetType="DataGridCell">
                    <Style.Triggers>
                        <DataTrigger Binding="{Binding column4}" Value="232">
                            <Setter Property="Background" Value="Red"/>
                        </DataTrigger>
                    </Style.Triggers>
                </Style>
            </DataGridTextColumn.CellStyle>
        </DataGridTextColumn>
        <!--...-->
    </DataGrid.Columns>
    <!--...-->
</DataGrid>

默认情况下，DataGrid 使用虚拟化，因此只会加载用户当前可见的 DataGridRows.其他行将在它们可见后创建，因此如果您尝试在后面的代码中设置某些单元格的样式可能会变得非常混乱(您尝试访问的单元格甚至可能还不存在.)

By default, the DataGrid is using virtualization so only the DataGridRows that are visible to the user at the moment will be loaded. The other rows will be created once they become visible so if you're trying to style some cells in code behind in can become pretty messy (the cell you are trying to access might not even exist yet.)

要在索引行/列处获得 DataGridCell，您可以定义一个辅助类 (DataGridHelper) 并像这样使用它

To get a DataGridCell at index row/column you can define a helper class (DataGridHelper) and use it like this

DataGridCell cell = DataGridHelper.GetCell(dataGrid, 0, 2);
if (cell != null)
{
    cell.Background = Brushes.Red;
}

DataGridHelper

static class DataGridHelper
{
    static public DataGridCell GetCell(DataGrid dg, int row, int column)
    {
        DataGridRow rowContainer = GetRow(dg, row);

        if (rowContainer != null)
        {
            DataGridCellsPresenter presenter = GetVisualChild<DataGridCellsPresenter>(rowContainer);

            // try to get the cell but it may possibly be virtualized
            DataGridCell cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(column);
            if (cell == null)
            {
                // now try to bring into view and retreive the cell
                dg.ScrollIntoView(rowContainer, dg.Columns[column]);
                cell = (DataGridCell)presenter.ItemContainerGenerator.ContainerFromIndex(column);
            }
            return cell;
        }
        return null;
    }

    static public DataGridRow GetRow(DataGrid dg, int index)
    {
        DataGridRow row = (DataGridRow)dg.ItemContainerGenerator.ContainerFromIndex(index);
        if (row == null)
        {
            // may be virtualized, bring into view and try again
            dg.ScrollIntoView(dg.Items[index]);
            row = (DataGridRow)dg.ItemContainerGenerator.ContainerFromIndex(index);
        }
        return row;
    }

    static T GetVisualChild<T>(Visual parent) where T : Visual
    {
        T child = default(T);
        int numVisuals = VisualTreeHelper.GetChildrenCount(parent);
        for (int i = 0; i < numVisuals; i++)
        {
            Visual v = (Visual)VisualTreeHelper.GetChild(parent, i);
            child = v as T;
            if (child == null)
            {
                child = GetVisualChild<T>(v);
            }
            if (child != null)
            {
                break;
            }
        }
        return child;
    }
}