Interface IEvaluatesDomValueExpression

An object which evaluates an expression and returns a value which may be used by the DOM.

Namespace: ZptSharp.Tal

Assembly: ZptSharp.Abstractions.dll

Syntax

public interface IEvaluatesDomValueExpression

Methods

EvaluateExpressionAsync(String, ExpressionContext, CancellationToken)

Evaluates the expression asynchronously and returns the result.

Declaration

Task<DomValueExpressionResult> EvaluateExpressionAsync(string expression, ExpressionContext context, CancellationToken cancellationToken = default(CancellationToken))

Parameters

Type	Name	Description
System.String	expression	An expression which might be prefixed to indicate that it is to be treated as structure.
ExpressionContext	context	Context.
System.Threading.CancellationToken	cancellationToken	Cancellation token.

Returns

Type	Description
System.Threading.Tasks.Task<DomValueExpressionResult>	The expression result.

Remarks

This method also deals with the differentiation between structure and text expressions. Structure expressions are inserted directly into the DOM without escaping or encoding. Text expressions are treated explicitly as text and are encoded/escaped to ensure that they are not accidentally treated as markup.

Expressions are treated as text by default. An expression is only treated as structure if:

• It is prefixed by a keyword structure and a single space, for example structure myExpression
• The expression result implements IGetsStructuredMarkup and the expression is NOT prefixed by the keyword text and a single space, for example text myExpression

Apart from aborting the treatment of IGetsStructuredMarkup as structure, the text prefix keyword for expressions is redundant, as it is the default. It is supported though, for situations where you wish to be explicit.