NPOI DataFormat

Question

我正在使用NPOI v1.2.3导出网格,并且无法使单元格格式化工作.

我有一个类将对象列表导出到XLS文件.为每个对象创建一行,并为每个已配置的属性添加一个单元格.可以在每个属性级别上设置单元格数据格式.

我读过你不应该为每个单元格创建一个新的样式.我无法对我的样式进行硬编码,因为我的导出器需要支持任何类.相反,我编写了一个小缓存系统,只有在尚未为当前单元格格式创建的情况下才创建新的CellStyle.

不幸的是,这仍然没有解决问题.格式未在最终的XLS文件中正确应用.在我的测试用例中,XLS中的大多数单元格都使用"日期"格式,即使只有几列是日期.但是,第一列正确使用自定义格式.没有单元格设置为文本,即使它应该是大多数单元格.

我究竟做错了什么？

码

下面的"AddRecords"方法用于添加数据行(页眉和页脚行分别添加).最后一段代码是延迟加载CellStyles的方法.

private void AddRecords( Sheet sheet, IList<T> records )
{
    foreach( var record in records )
    {
        // append row
        var row = sheet.CreateRow ( sheet.LastRowNum + 1 );

        // iterate through all configured columns
        foreach ( var column in GetColumns() )
        {
            // append cell
            Cell cell = row.CreateCell ( row.LastCellNum == -1 ? 0 : row.LastCellNum );

            // get the property value of the column from the record
            object value = GetCellValue ( column, record );

            // extension method that takes an object value and calls the appropriate type-specific SetCellValue overload
            cell.SetCellValue ( value );

            // get format from the column definition ("m/d", "##.###", etc.), or use the default
            string dataFormat = column.DataFormat ?? GetDefaultDataFormat ( value );

            // find/create cell style
            cell.CellStyle = GetCellStyleForFormat( sheet.Workbook, dataFormat );
        }
    }
}

/// <summary>
/// Returns a default format string based on the object type of value.
///
/// http://poi.apache.org/apidocs/org/apache/poi/ss/usermodel/BuiltinFormats.html
/// </summary>
/// <param name="value"></param>
/// <returns></returns>
private string GetDefaultDataFormat( object value )
{
    if( value == null )
    {
        return "General";
    }

    if( value is DateTime )
    {
        return "m/d";
    }

    if( value is bool )
    {
        return "[=0]\"Yes\";[=1]\"No\"";
    }

    if( value is byte || value is ushort || value is short ||
         value is uint || value is int || value is ulong || value is long )
    {
        return "0";
    }

    if( value is float || value is double )
    {
        return "0.00";
    }

    // strings and anything else should be text
    return "text";
}

private readonly Dictionary<string, CellStyle> _cellStyleCache = new Dictionary < string, CellStyle > ();

private CellStyle GetCellStyleForFormat( Workbook workbook, string dataFormat )
{
    if( !_cellStyleCache.ContainsKey ( dataFormat ) )
    {
        var newDataFormat = workbook.CreateDataFormat ();
        var style = workbook.CreateCellStyle ();
        style.DataFormat = newDataFormat.GetFormat ( dataFormat );

        _cellStyleCache[dataFormat] = style;
    }

    return _cellStyleCache[dataFormat];
}

Answer 1

看起来这个问题与创建与内置格式匹配的新格式有关.我改变了我的延迟加载方法以使用内置格式(如果可用),并且我最终XLS中的单元格格式现在都是正确的.

if( !_cellStyleCache.ContainsKey ( dataFormat ) )
{
    var style = workbook.CreateCellStyle ();

    // check if this is a built-in format
    var builtinFormatId = HSSFDataFormat.GetBuiltinFormat ( dataFormat );

    if( builtinFormatId != - 1)
    {
        style.DataFormat = builtinFormatId;
    }
    else
    {
        // not a built-in format, so create a new one
        var newDataFormat = workbook.CreateDataFormat ();
        style.DataFormat = newDataFormat.GetFormat ( dataFormat );
    }

    _cellStyleCache[dataFormat] = style;
}