如何在FlowDocument中设置A4页面宽度，解决打印时第四列缺失问题

问题根源 #

你遇到的打印列显示异常是3个核心原因共同导致的：

• FlowDocument默认带了左右页边距，你直接把PageWidth设为打印区域宽度后，实际表格可用宽度要小于设置值，固定像素的列宽总和超出可用宽度后第四列就会被裁切
• 你设置的四列固定像素宽度（总460px）加单元格间距后，已经接近A4纸横向打印一半宽度，和你观察到的「页面仅占A4一半」的现象吻合
• 你的代码存在两个逻辑错误：取行索引偏移、重复添加同一个Paragraph实例，也会引发渲染异常

修复步骤 #

1. 先清空FlowDocument默认页边距，避免可用宽度被占用

FlowTabledoc.PagePadding = new Thickness(0);
// 如果需要留边，可设置为 new Thickness(10,5,10,5) 对应左、上、右、下的边距

2. 列宽改用比例分配，不要用固定像素，保证永远适配页面可用宽度

// 按你原来的列宽比例分配，自动适配整个打印宽度，不会超出也不会留空白
logflowtable.Columns[0].Width = new GridLength(60.0, GridUnitType.Star); 
logflowtable.Columns[1].Width = new GridLength(120.0, GridUnitType.Star);
logflowtable.Columns[2].Width = new GridLength(190.0, GridUnitType.Star);
logflowtable.Columns[3].Width = new GridLength(90.0, GridUnitType.Star);

3. 修正代码逻辑错误

// 取行索引不要加1，刚添加的行索引就是当前r值
currentRow = logflowtable.RowGroups[0].Rows[r];

// 不要重复添加同一个Paragraph实例，需要空行的话每次实例化新对象
FlowTabledoc.Blocks.Add(new Paragraph() { FontSize =14 });

4. 可选：如果要固定A4尺寸打印，显式设置页面尺寸即可

// A4纸对应WPF单位（96DPI）的宽高
FlowTabledoc.PageWidth = 793.7;
FlowTabledoc.PageHeight = 1122.5;

完整可运行代码参考 #

PrintDialog printDlg = new PrintDialog();
FlowDocument FlowTabledoc = new FlowDocument();
// 清空默认边距
FlowTabledoc.PagePadding = new Thickness(0);
FlowTabledoc.PageWidth = printDlg.PrintableAreaWidth;

Table logflowtable = new Table();
FlowTabledoc.Blocks.Add(logflowtable);
logflowtable.CellSpacing = 5;

int numberOfColumns = 4;
for (int x = 0; x < numberOfColumns; x++)
{
    logflowtable.Columns.Add(new TableColumn());
}
// 比例分配列宽
logflowtable.Columns[0].Width = new GridLength(60.0, GridUnitType.Star); 
logflowtable.Columns[1].Width = new GridLength(120.0, GridUnitType.Star);
logflowtable.Columns[2].Width = new GridLength(190.0, GridUnitType.Star);
logflowtable.Columns[3].Width = new GridLength(90.0, GridUnitType.Star);

logflowtable.RowGroups.Add(new TableRowGroup());

int RowAnzahl = LogTB.Rows.Count;
int ColAnzahl = LogTB.Columns.Count;

for (int r = 0; r <= RowAnzahl - 1; r++)
{
    logflowtable.RowGroups[0].Rows.Add(new TableRow());
    // 修正索引
    TableRow currentRow = logflowtable.RowGroups[0].Rows[r];
    currentRow.FontSize = 14;
    currentRow.FontWeight = FontWeights.Normal;
    
    for (int c = 0; c <= ColAnzahl - 1; c++)
    {
        currentRow.Cells.Add(new TableCell(new Paragraph(new Run(LogTB.Rows[r][c].ToString()))));
    }
    // 每次新建空段落
    FlowTabledoc.Blocks.Add(new Paragraph() { FontSize =14 });
}

FlowTabledoc.Name = "FlowDoc";
IDocumentPaginatorSource idpSource = FlowTabledoc;
printDlg.PrintDocument(idpSource.DocumentPaginator, "Title-Header");

内容的提问来源于stack exchange，提问作者HothCoder