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HTML Export

Mats Alm edited this page Jun 18, 2024 · 39 revisions

EPPlus 6 introduces the ability to export a table or a range to HTML/CSS. The best way to get started with this functionality is to have a look at the examples in our web samples project

Overview

This feature supports integration of spreadsheet data and styling into web applications - and it is not an implementation of Excel's "Save the workbook as html" feature. Our intention is to make EPPlus a useful tool for bringing the spreadsheet model to web applications rather than providing a pixel-perfect html-representation of an existing workbook.

Html

The spreadsheet data is always exported as a html table. The html has support for accessibility (aria-*) attributes that can be configured when exporting the data. You can also get the raw cell data and javascript compatible datatypes included via data-* attributes in order to use the exported table not only as a UI element but also as a data carrier.

Style/css

EPPlus separates styling from html and creates a separate stylesheet (css) for the exported data. The classes in this stylesheet are created based on the internal Excel styles. This is per default based on the built in Office theme, but you can easily switch to another theme as demonstrated our html sample 1. EPPlus will export css for table styles when exporting a table. NOTE: Exporting a range that contains a table will not include the table styles in the css.

Pictures/Images

Images in the cells will be included by default as base64 encoded strings in the stylesheet. Images are per default not included in the export, for more details see this chapter.

Limitations

We will add new features to this export over time, but please note that some Excel features such as charts, shapes, pivot tables, sparklines and threaded comments are included in the export. Full support for conditional formatting was added in version 7.2.

Basic usage

Create Html exporter

You can export html/css either from a range or from a a table in your workbook. This is done via the CreateHtmlExporter() function, see below:
Please note that table styles are not included in the css, if you export a range that contains a table via the ExcelRangeBase.CreateHtmlExporter().

Export from a range

var exporter = sheet.Cells["B5:M19"].CreateHtmlExporter();
var html = exporter.GetHtmlString();
var css = exporter.GetCssString();

Export from a table

This export will contain the css for the table style as well as any cell style css.

var exporter = sheet.Tables[0].CreateHtmlExporter();
var html = exporter.GetHtmlString();
var css = exporter.GetCssString();

Export multiple ranges

You can also create an exporter for several ranges at once to get a shared css for multiple ranges over multiple worksheets. Our web sample 6 shows how to do this in detail.

var exporter = package.Workbook.CreateHtmlExporter(
                 package.Workbook.Worksheet[0].Cells["B5:M19"],
                 package.Workbook.Worksheet[1].Cells["A1:D35"]
);

//This will get the html for the first range, B5:M19  in the first sheet
var html1 = exporter.GetHtmlString(0);
//This will get the html for the first range, A1:D35 in the second sheet
var html2 = exporter.GetHtmlString(1);
//This gets the combined css for both ranges.
var css = exporter.GetCssString();

Methods

There are async versions of GetHtmlString() and GetCssString(), suffixed with "Async". Other methods renders html and css on a System.IO.Stream, see RenderHtml(stream), RenderHtmlAsync(stream), RenderCss(stream) and RenderCssAsync(stream).

Table Id and addtional table classes

Use the properties below to set the id attribute and add additional css classes on the exported html table.

var settings = exporter.Settings;
settings.TableId = "currency-table";
settings.AdditionalTableClassNames.Add("table");
settings.AdditionalTableClassNames.Add("table-sm");
settings.AdditionalTableClassNames.Add("table-borderless");

Exporter.Settings

Via the Settings property on the exporter you can control how the html is exported. This class has the following properties:

Property Data type Default value Description
TableId string null id of the table html element
Minify bool true If true the html will not contain indents and linebreaks.
HiddenRows eHiddenState Exclude Controls how hidden cells are exported. One of the following: Exclude, IncludeButHide, Include
HorizontalAlignmentWhenGeneral eHtmlGeneral-AlignmentHandling CellDataType Controls alignment when a cells style is set to General. One of the following: DontSet, ColumnDataType (if the cell value data type is numeric or date, alignment will be right otherwise left), CellDataType (if the cell value data type is numeric or date, alignment will be right otherwise left)
Accessibility AccessibilitySettings N/A See Accessibility attributes below
AdditionalTableClassNames List<string> The list is empty Here you can add additional class names that will be added to the exported tables class attribute
Culture CultureInfo CurrentCulture The culture used when formatting the cell output.
Encoding Encoding Encoding.UTF8 Encoding for the output
SetColumnWidth bool false Set the column width for columns in the table via the columngroup/col element. Columns with the default width will have the default column width class set. Columns with custom column width will have the width set directly via the style attribute.
SetRowHeight bool false Set the row height for rows in the table. Rows with the default height will have the default row height class set. Rows with custom row height will have the height set directly via the style attribute.
StyleClassPrefix string epp- Prefix for style classes added by EPPlus.
CellStyleClassName string s The name used for cell style css classes. Cell style css classes will be named {StyleClassPrefix}{CellStyleClassName}{index}
IncludePictures bool false If pictures in cells should be included
IncludeCssClassNames bool true If true the exported html will include css class names that refers to exported css.
RenderDataAttributes bool true If true raw cell data values will be included in the data-value attribute
RenderDataTypes bool true If true data types will be included in the data-datatype attribute

Exporter.Settings.Css

Settings controling the css output.

Property Data type Default value Description
CssExclude CssExclude Properties to exclude specific styles from the css.
AdditionalCssElements Dictionary<string,string> empty Add additional css elements to the default table style. For example exporter.Settings.Css.AdditionalCssElements.Add("font-family", "verdana");
IncludeSharedClasses bool true If the css should include shared styles used for the exported table.
IncludeNormalFont bool true If the normal font name and size should be included in the css for the table.
IndentValue float 2 The value for indented cells.
IndentUnit string em The unit for indented cells.

Exporter.Settings.Pictures

Pictures/images are not exported per default, but this can be enabled like this:

exporter.Settings.Pictures.Include = ePictureInclude.Include;

The ePictureInclude enum has three members: Exclude (pictures will not be included), IncludeInCssOnly (pictures will be included in css only, so they can be added manually) and Include.

Here are the parameters you can set via the Exporter.Settings.Picture property.

Property Data type Default value Description
Include ePictureInclude Exclude Sets if and how pictures should be included.
Position ePicturePosition Relative Possible values: DontSet, Absolute or Relative
AddMarginTop bool false If the margin in pixels from the left corner should be used.
AddMarginLeft bool false If the margin in pixels from the top corner should be used
KeepOriginalSize bool false If set to true the original size of the image is used, otherwise the size in the workbook is used
CssExclude PictureCssExclude N/A With this property you can exclude certain parts from the exported css, such as border and alignment

The data-* attributes

In html you can add custom attributes that is prefixed with "data-". In EPPlus we have added two attributes to the exported table elements: data-value and data-datatype.

Our web sample 4 demonstrates how these attributes can be used.

data-datatype

This attribute is added either on the table.thead.tr.th element or on the table.tbody.tr.td element. See the table below for how the .NET datatypes from EPPlus are mapped to the exported html.

.NET data type Exported datatype name Comment
bool boolean Exported as 1/0
Byte, Sbyte, UInt16, UInt32, UInt64, Int16, Int32, Int64, Decimal, Double, Single (float) number All types mapped to the single number datatype
DateTime datetime Exported to milliseconds before/after January 1, 1970 (Linux/Unix epoch).
TimeSpan timespan Exported as a numeric value, total milliseconds after midnight
string (and all other datatypes) string Exported as-is

See below how the data-datatype attribute is included in the html of an exported table.

<thead role="rowgroup">
    <tr role="row">
      <th data-datatype="string" class="epp-al" role="columnheader" scope="col">Country</th>
      <th data-datatype="string" class="epp-al" role="columnheader" scope="col">FirstName</th>
      <th data-datatype="string" class="epp-al" role="columnheader" scope="col">LastName</th>
      <th data-datatype="datetime" class="epp-al" role="columnheader" scope="col">BirthDate</th>
      <th data-datatype="string" class="epp-al" role="columnheader" scope="col">City</th>
    </tr>
  </thead>

data-value

This attribute will contain the raw value of the cell, see the datatypes table above. Here is an example:

<tr role="row" scope="row">
  <td role="cell">Scotland</td>
  <td role="cell">Autumn</td>
  <td role="cell">Toy</td>
  <td data-value="-1485302400000" role="cell" class="epp-ar">1922-12-08</td>
  <td role="cell">New Andrewhaven</td>
</tr>

Note that this attribute is only present if the raw value differs from the formatted value (the content of the td element).

Accessibility attributes

Accessibility attributes are included by default. Here is an example on how to set the aria-label attribute on the exported table:

var exporter = sheet.Cells["B5:M19"].CreateHtmlExporter();
exporter.Settings.Accessibility.TableSettings.AriaLabel = "This html-table is exported from EPPlus";

results in:

<table class="epplus-table" role="table" aria-label="This html-table is exported from EPPlus">

If you don't want to include accessibility attributes in the html set the below property to false:

exporter.Settings.Accessibility.TableSettings.AddAccessibilityAttributes = false;

Via the exporter's Settings.Accessibility.TableSettings property you can set the following attributes:

EPPlus attribute Html attribute Html element Default value
AriaLabel aria-label table null
AriaLabelledBy aria-labelledby table null
AriaDescribedBy aria-describedby table null
TableRole role table table
TheadRole role table.thead rowgroup
TbodyRole role table.tbody rowgroup
TfootRole role table.tfoot rowgroup
TableHeaderCellRole role table.thead.tr.th columnheader

See also

EPPlus wiki

Versions

Worksheet & Ranges

Styling

Import/Export data

Formulas and filters

Charts & Drawing objects

Tables & Pivot Tables

VBA & Protection

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