Basic Template Syntax - Expression Tags and Fields Leave feedback

GroupDocs.Assembly for .NET uses a simple, LINQ-based template syntax that allows you to embed C# expressions directly in your documents. Expression tags are the foundation of template syntax, enabling you to output data values and perform calculations.

The main syntax elements are:

• Expression tags <<[expression]>> - output expression results
• Data bands <<foreach>> - iterate over collections
• Conditional blocks <<if>> - display content conditionally

Here are the steps to use basic template syntax:

• Create a template document in Word, Excel, PowerPoint, or HTML format
• Insert expression tags using <<[expression]>> syntax
• Reference data source properties and methods in expressions
• Assemble the document with your data source

Note

Template syntax is case-sensitive and follows C# language rules. Expression tags are evaluated at runtime and replaced with their computed values.

Expression tags are the simplest way to output data in templates. They use the syntax <<[expression]>>:

using GroupDocs.Assembly;

public static void BasicExpressionTags()
{
    // Sample data
    var person = new { Name = "John Doe", Age = 30, Email = "john@example.com" };
    
    // Assemble document
    DocumentAssembler assembler = new DocumentAssembler();
    assembler.AssembleDocument("Template.docx", "Output.docx", 
        new DataSourceInfo(person, "person"));
    
    Console.WriteLine("Document assembled with expression tags.");
}

In your template document (Template.docx), use expression tags like this:

Name: <<[person.Name]>>
Age: <<[person.Age]>>
Email: <<[person.Email]>>

After assembly, the output will be:

Name: John Doe
Age: 30
Email: john@example.com

When using a single data source, you can omit the data source name and use contextual access:

using GroupDocs.Assembly;

public static void ContextualAccess()
{
    var product = new { Name = "Laptop", Price = 999.99m, Stock = 50 };
    
    DocumentAssembler assembler = new DocumentAssembler();
    assembler.AssembleDocument("Template.docx", "Output.docx", 
        new DataSourceInfo(product));
    
    Console.WriteLine("Document assembled with contextual access.");
}

Template with contextual access:

Product: <<[Name]>>
Price: <<[Price]>>
Stock: <<[Stock]>>

You can perform calculations directly in expression tags:

using GroupDocs.Assembly;

public static void CalculationsInExpressions()
{
    var order = new { Quantity = 5, UnitPrice = 29.99m };
    
    DocumentAssembler assembler = new DocumentAssembler();
    assembler.AssembleDocument("Template.docx", "Output.docx", 
        new DataSourceInfo(order, "order"));
    
    Console.WriteLine("Document assembled with calculations.");
}

Template with calculations:

Quantity: <<[order.Quantity]>>
Unit Price: <<[order.UnitPrice]>>
Total: <<[order.Quantity * order.UnitPrice]>>

You can use .NET string methods in expressions:

using GroupDocs.Assembly;

public static void StringMethods()
{
    var company = new { Name = "ABC Corporation", Website = "www.example.com" };
    
    DocumentAssembler assembler = new DocumentAssembler();
    assembler.AssembleDocument("Template.docx", "Output.docx", 
        new DataSourceInfo(company, "company"));
    
    Console.WriteLine("Document assembled with string methods.");
}

Template with string methods:

Company: <<[company.Name.ToUpper()]>>
Website: <<[company.Website.ToLower()]>>

You can format expression results using format strings:

using GroupDocs.Assembly;

public static void FormattedExpressions()
{
    var invoice = new { 
        Amount = 1500.50m, 
        Date = new DateTime(2024, 1, 15),
        Percentage = 0.15
    };
    
    DocumentAssembler assembler = new DocumentAssembler();
    assembler.AssembleDocument("Template.docx", "Output.docx", 
        new DataSourceInfo(invoice, "invoice"));
    
    Console.WriteLine("Document assembled with formatting.");
}

Template with formatting:

Amount: <<[invoice.Amount]:"C">>
Date: <<[invoice.Date]:"yyyy-MM-dd">>
Percentage: <<[invoice.Percentage]:"P">>

Warning

Format strings follow .NET formatting conventions. Use “C” for currency, “P” for percentage, and standard date/time format strings for dates.

To learn more about data bands, conditional blocks, LINQ expressions, and advanced template syntax features, please refer to the advanced usage section.

You may easily run the code above and see the feature in action in our GitHub examples:

• GroupDocs.Assembly for .NET examples, plugins, and showcase
• GroupDocs.Assembly for Java examples, plugins, and showcase
• GroupDocs.Assembly for Python via .NET examples, plugins, and showcase

Along with the full-featured .NET library, we provide simple but powerful free online apps.

To assemble documents from templates and data sources, you can use the online apps from the GroupDocs.Assembly App Product Family.