Automate Presentation Localization in .NET

What this page is about

Set proofing languages for PowerPoint and OpenDocument presentation text in .NET with Aspose.Slides, including defaults and multilingual paragraphs.

Overview

Aspose.Slides for .NET lets you configure proofing metadata for individual text portions. Use IBasePortionFormat.LanguageId to identify the proofing language, BasePortionFormat.SpellCheck to allow or suppress spelling checks, and BasePortionFormat.ProofDisabled to control the broader no-proof state. Because these settings are applied at the portion level, one paragraph can contain multiple languages and different proofing rules.

This article explains how to assign a language to specific text, set the default language for new text with LoadOptions.DefaultTextLanguage, build multilingual paragraphs, choose between SpellCheck and ProofDisabled, and preserve the intended settings when using Presentation.JoinPortionsWithSameFormatting. These properties store metadata for presentation applications; they do not translate text, perform dictionary-based spell checking, or return misspelled words.

Set the Proofing Language for Text

Create or load a Presentation, access the required text portion through IPortion.PortionFormat, and assign its language identifier. The following example creates a shape, sets British English as the proofing language, and saves the result with Presentation.Save:

using Aspose.Slides;
using Aspose.Slides.Export;

using var presentation = new Presentation();
var slide = presentation.Slides[0];
var shape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 50, 50, 320, 80);
shape.TextFrame.Text = "Set the proofing language for this text.";

var portion = shape.TextFrame.Paragraphs[0].Portions[0];
portion.PortionFormat.LanguageId = "en-GB";

presentation.Save("proofing_language.pptx", SaveFormat.Pptx);

Set the Default Language for New Text

Use LoadOptions.DefaultTextLanguage to specify the proofing language that Aspose.Slides assigns to newly created text. This setting is useful when most or all new text in a presentation uses the same language. It does not change the language metadata of text that already has an explicit language.

The following example creates a presentation whose new text uses German proofing rules:

using Aspose.Slides;
using Aspose.Slides.Export;

var loadOptions = new LoadOptions
{
    DefaultTextLanguage = "de-DE"
};

using var presentation = new Presentation(loadOptions);
var slide = presentation.Slides[0];
var shape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 50, 50, 320, 80);
shape.TextFrame.Text = "Willkommen zur Präsentation";

presentation.Save("default_text_language.pptx", SaveFormat.Pptx);

Use Multiple Languages in One Paragraph

An IParagraph contains a collection of text portions. Create a separate Portion for each language and set its LanguageId independently.

This example creates one paragraph with English and French portions:

using Aspose.Slides;
using Aspose.Slides.Export;

using var presentation = new Presentation();
var slide = presentation.Slides[0];
var shape = slide.Shapes.AddAutoShape(ShapeType.Rectangle, 50, 50, 420, 80);
var paragraph = shape.TextFrame.Paragraphs[0];
paragraph.Portions.Clear();

var englishPortion = new Portion("Welcome");
englishPortion.PortionFormat.LanguageId = "en-US";
paragraph.Portions.Add(englishPortion);

var frenchPortion = new Portion(" — Bienvenue");
frenchPortion.PortionFormat.LanguageId = "fr-FR";
paragraph.Portions.Add(frenchPortion);

presentation.Save("multilingual_text.pptx", SaveFormat.Pptx);

Enable or Suppress Spell Checking for Individual Portions

IPortionFormat inherits the common text properties defined by IBasePortionFormat. Access a portion’s format through IPortion.PortionFormat and set BasePortionFormat.SpellCheck to control whether a presentation application may check spelling for that portion. The default value is false: true allows spell checking, while false suppresses it.

The setting applies to individual text portions. Different portions in the same paragraph can therefore use different values. BasePortionFormat.LanguageId and SpellCheck serve complementary purposes: LanguageId identifies the proofing language, while SpellCheck determines whether spelling checks are allowed for the portion.

BasePortionFormat.ProofDisabled also controls proofing, but it represents the broader “do not proof” state as a NullableBool. Use SpellCheck when you need a direct Boolean switch specifically for spelling checks. Use ProofDisabled when you need to preserve or explicitly control the presentation’s no-proof metadata, including its NotDefined state. If you set both properties, keep their values consistent; do not combine SpellCheck = true with ProofDisabled = NullableBool.True.

These properties configure proofing metadata used by PowerPoint and other presentation applications. Aspose.Slides does not use them to run dictionary-based spell checking or return a list of misspelled words.

The following complete example creates an input presentation, loads it, assigns different spell-check settings and proofing languages to two portions in the same paragraph, saves the result, reopens it, and verifies the stored values:

using System;
using Aspose.Slides;
using Aspose.Slides.Export;

const string inputFile = "spell_check_input.pptx";
const string outputFile = "spell_check_settings.pptx";

using (var sourcePresentation = new Presentation())
{
    var sourceSlide = sourcePresentation.Slides[0];
    var sourceShape = sourceSlide.Shapes.AddAutoShape(ShapeType.Rectangle, 50, 50, 420, 80);
    var sourceParagraph = sourceShape.TextFrame.Paragraphs[0];
    sourceParagraph.Portions.Clear();

    var sourceEnglishPortion = new Portion("Check this text. ");
    sourceEnglishPortion.PortionFormat.LanguageId = "en-US";
    sourceParagraph.Portions.Add(sourceEnglishPortion);

    var sourceFrenchPortion = new Portion("Ignorer ce code : ZX-81.");
    sourceFrenchPortion.PortionFormat.LanguageId = "fr-FR";
    sourceParagraph.Portions.Add(sourceFrenchPortion);

    sourcePresentation.Save(inputFile, SaveFormat.Pptx);
}

using (var presentation = new Presentation(inputFile))
{
    var shape = (IAutoShape)presentation.Slides[0].Shapes[0];
    var portions = shape.TextFrame.Paragraphs[0].Portions;

    var checkedPortion = portions[0];
    checkedPortion.PortionFormat.LanguageId = "en-US";
    checkedPortion.PortionFormat.SpellCheck = true;

    var suppressedPortion = portions[1];
    suppressedPortion.PortionFormat.LanguageId = "fr-FR";
    suppressedPortion.PortionFormat.SpellCheck = false;

    presentation.Save(outputFile, SaveFormat.Pptx);
}

using var reopenedPresentation = new Presentation(outputFile);
var reopenedShape = (IAutoShape)reopenedPresentation.Slides[0].Shapes[0];
var storedPortions = reopenedShape.TextFrame.Paragraphs[0].Portions;

var firstPortionStored = storedPortions.Count == 2 &&
    storedPortions[0].PortionFormat.LanguageId == "en-US" &&
    storedPortions[0].PortionFormat.SpellCheck;

var secondPortionStored = storedPortions.Count == 2 &&
    storedPortions[1].PortionFormat.LanguageId == "fr-FR" &&
    !storedPortions[1].PortionFormat.SpellCheck;

if (firstPortionStored && secondPortionStored)
{
    Console.WriteLine("The proofing settings were stored correctly.");
}
else
{
    Console.WriteLine("The proofing settings could not be verified.");
}

Presentation.JoinPortionsWithSameFormatting combines adjacent portions that have the same formatting. A difference in SpellCheck alone does not keep such portions separate; after they are joined, the resulting portion retains the SpellCheck value of the first portion. If portions need different spell-check settings, call JoinPortionsWithSameFormatting before assigning those settings, or inspect the resulting portion boundaries and reapply the settings afterward. Portions with different LanguageId values remain separate because their proofing-language formatting differs.

FAQ

Does a language ID translate the text?

No. IBasePortionFormat.LanguageId stores proofing metadata for spelling and grammar; it does not alter the text content. Translate the text separately, and then set the appropriate language identifier for each translated portion.

Does the proofing language control fonts, hyphenation, or line wrapping?

No. The language identifier is for proofing. Text rendering and layout primarily depend on the available fonts, the writing system, and the text-frame settings. For reliable rendering, provide the required fonts, configure font substitution, or embed fonts in the presentation.

Can one paragraph use several proofing languages?

Yes. Assign each language to a separate portion, as shown in the multilingual paragraph example.

Should I use DefaultTextLanguage or LanguageId?

Use LoadOptions.DefaultTextLanguage when you want a default for newly created text. Use IBasePortionFormat.LanguageId when a specific portion needs an explicit proofing language or when a paragraph contains multiple languages.

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