public static bool ExtractNullPropagationExpression(ConditionalExpression conditionalExpression, out List <Expression> nullTestExpressions, out Expression ifNotNullExpression)
{
if (conditionalExpression == null)
{
throw new ArgumentNullException("conditionalExpression");
}
nullTestExpressions = null;
ifNotNullExpression = null;
if (TryExtractTestTargets(conditionalExpression.Test, ref nullTestExpressions) == false)
{
return(false);
}
if (nullTestExpressions == null || nullTestExpressions.Count == 0)
{
return(false);
}
var ifFalseConst = conditionalExpression.IfFalse as ConstantExpression;
var ifTrueUnwrapped = conditionalExpression.IfTrue.NodeType == ExpressionType.Convert ? ((UnaryExpression)conditionalExpression.IfTrue).Operand : conditionalExpression.IfTrue;
// try to detect null-propagation operation
if (ifFalseConst == null || ifFalseConst.Value != null || ExpressionLookupVisitor.Lookup(conditionalExpression.IfTrue, nullTestExpressions) == false)
{
return(false);
}
ifNotNullExpression = ifTrueUnwrapped;
return(true);
}
public static bool Lookup(Expression expression, List <Expression> lookupList)
{
var visitor = new ExpressionLookupVisitor(lookupList);
visitor.Visit(expression);
return(visitor.found == lookupList.Count);
}
