/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <param name="ifFalse">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfFalse"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// and <see cref="P:ConditionalExpression.IfFalse"/> properties set to the specified values.</returns>
public static ConditionalExpression Condition(Expression test, Expression ifTrue, Expression ifFalse)
{
RequiresCanRead(test, "test");
RequiresCanRead(ifTrue, "ifTrue");
RequiresCanRead(ifFalse, "ifFalse");
if (test.Type != typeof(bool))
{
throw Error.ArgumentMustBeBoolean();
}
if (!TypeUtils.AreEquivalent(ifTrue.Type, ifFalse.Type))
{
throw Error.ArgumentTypesMustMatch();
}
return(ConditionalExpression.Make(test, ifTrue, ifFalse, ifTrue.Type));
}
// ConditionalExpression
private Result RewriteConditionalExpression(Expression expr, Stack stack)
{
ConditionalExpression node = (ConditionalExpression)expr;
// Test executes at the stack as left by parent
Result test = RewriteExpression(node.Test, stack);
// The test is popped by conditional jump so branches execute
// at the stack as left by parent too.
Result ifTrue = RewriteExpression(node.IfTrue, stack);
Result ifFalse = RewriteExpression(node.IfFalse, stack);
RewriteAction action = test.Action | ifTrue.Action | ifFalse.Action;
if (action != RewriteAction.None)
{
expr = ConditionalExpression.Make(test.Node, ifTrue.Node, ifFalse.Node, node.Type);
}
return(new Result(action, expr));
}
/// <summary>
/// Creates a <see cref="ConditionalExpression"/>.
/// </summary>
/// <param name="test">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.Test"/> property equal to.</param>
/// <param name="ifTrue">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfTrue"/> property equal to.</param>
/// <param name="ifFalse">An <see cref="Expression"/> to set the <see cref="P:ConditionalExpression.IfFalse"/> property equal to.</param>
/// <param name="type">A <see cref="Type"/> to set the <see cref="P:Expression.Type"/> property equal to.</param>
/// <returns>A <see cref="ConditionalExpression"/> that has the <see cref="P:Expression.NodeType"/> property equal to
/// <see cref="F:ExpressionType.Conditional"/> and the <see cref="P:ConditionalExpression.Test"/>, <see cref="P:ConditionalExpression.IfTrue"/>,
/// and <see cref="P:ConditionalExpression.IfFalse"/> properties set to the specified values.</returns>
/// <remarks>This method allows explicitly unifying the result type of the conditional expression in cases where the types of <paramref name="ifTrue"/>
/// and <paramref name="ifFalse"/> expressions are not equal. Types of both <paramref name="ifTrue"/> and <paramref name="ifFalse"/> must be implicitly
/// reference assignable to the result type. The <paramref name="type"/> is allowed to be <see cref="System.Void"/>.</remarks>
public static ConditionalExpression Condition(Expression test, Expression ifTrue, Expression ifFalse, Type type)
{
RequiresCanRead(test, "test");
RequiresCanRead(ifTrue, "ifTrue");
RequiresCanRead(ifFalse, "ifFalse");
ContractUtils.RequiresNotNull(type, "type");
if (test.Type != typeof(bool))
{
throw Error.ArgumentMustBeBoolean();
}
if (type != typeof(void))
{
if (!TypeUtils.AreReferenceAssignable(type, ifTrue.Type) ||
!TypeUtils.AreReferenceAssignable(type, ifFalse.Type))
{
throw Error.ArgumentTypesMustMatch();
}
}
return(ConditionalExpression.Make(test, ifTrue, ifFalse, type));
}