/// <summary>
/// Simplifies an expression tree by evaluating any branches of the tree that do not include
/// lambda parameter references. This will remove references to variables external to the lambda
/// by converting them to constants, perform arithmetic, and execute method calls as needed.
/// For example, a call to "str.ToUpper()" where string is an external variable would be simplified
/// to a <see cref="ConstantExpression"/> containing the uppercase version of str.
/// </summary>
/// <param name="expression">Expression to simplify.</param>
/// <returns>The simplified expression.</returns>
public static Expression Simplify(Expression expression)
{
if (expression == null)
{
throw new ArgumentNullException("expression");
}
var visitor = new LambdaSimplifyingExpressionVisitor();
expression = visitor.Visit(expression);
if (visitor._isEvaluatable)
{
// The entire tree can simplified
return(ConvertToConstant(expression));
}
else
{
return(expression);
}
}
protected override Expression VisitLambda <T>(Expression <T> node)
{
if (_parameter != null)
{
throw new NotSupportedException("Only one lambda expression is allowed in a subdocument path.");
}
_parameter = node.Parameters[0];
// Simplify the body before processing. This makes any external variable references constants, and also
// reduces any expressions that can be simplified.
var body = LambdaSimplifyingExpressionVisitor.Simplify(node.Body);
body = Visit(body);
if (!_parameterEncountered)
{
throw new NotSupportedException("The first statement in a subdocument path must be a reference to the lambda parameter.");
}
return(node.Update(body, node.Parameters));
}
/// <summary>
/// Simplifies an expression tree by evaluating any branches of the tree that do not include
/// lambda parameter references. This will remove references to variables external to the lambda
/// by converting them to constants, perform arithmetic, and execute method calls as needed.
/// For example, a call to "str.ToUpper()" where string is an external variable would be simplified
/// to a <see cref="ConstantExpression"/> containing the uppercase version of str.
/// </summary>
/// <param name="expression">Expression to simplify.</param>
/// <returns>The simplified expression.</returns>
public static Expression Simplify(Expression expression)
{
if (expression == null)
{
throw new ArgumentNullException("expression");
}
var visitor = new LambdaSimplifyingExpressionVisitor();
expression = visitor.Visit(expression);
if (visitor._isEvaluatable)
{
// The entire tree can simplified
return ConvertToConstant(expression);
}
else
{
return expression;
}
}