The\u00a0as operator is more efficient because it actually returns the cast value if the cast can be made successfully. The is operator returns only a Boolean value. It can therefore be used when we just want to determine an object’s type but do not have to actually cast it.<\/p>\n
Use the is operator to verify the type before performing a cast.<\/p>\n
Use the as operator and test for null\u00a0before referencing the variable.<\/p>\n
Use the as operator to test\u00a0an incompatible type.<\/p>\n
Use the as operator with a value type.\u00a0Note the implicit conversion to int? in\u00a0\u00a0the\u00a0\u00a0 method body.<\/p>\n
<\/p>\n
example–class SafeCasting
\n{
\nclass Animal
\n{
\npublic\u00a0void Eat() { Console.WriteLine(“Eating.”); }
\npublic\u00a0override\u00a0string ToString()
\n{
\nreturn\u00a0“I am an animal.”;
\n}
\n}
\nclass Mammal : Animal { }
\nclass Giraffe : Mammal { }<\/p>\n
class SuperNova { }<\/p>\n
static\u00a0void Main()
\n{
\nSafeCasting app = new SafeCasting();<\/p>\n
\/\/ Use the is operator to verify the type.\u00a0before performing a cast.
\nGiraffe g = new Giraffe();
\napp.UseIsOperator(g);<\/p>\n
\/\/ Use the as operator and test for null\u00a0before referencing the variable.
\napp.UseAsOperator(g);<\/p>\n
\/\/ Use the as operator to test\u00a0an incompatible type.
\nSuperNova sn = new SuperNova();
\napp.UseAsOperator(sn);<\/p>\n
\/\/ Use the as operator with a value type.
\n\/\/ Note the implicit conversion to int? in
\n\/\/ the method body.
\nint i = 5;
\napp.UseAsWithNullable(i);<\/p>\n
double d = 9.78654;
\napp.UseAsWithNullable(d);<\/p>\n
\/\/ Keep the console window open in debug mode.
\nSystem.Console.WriteLine(“Press any key to exit.”);
\nSystem.Console.ReadKey();
\n}<\/p>\n
void UseIsOperator(Animal a)
\n{
\nif (a is Mammal)
\n{
\nMammal m = (Mammal)a;
\nm.Eat();
\n}
\n}<\/p>\n
void UseAsOperator(object o)
\n{
\nMammal m = o as Mammal;
\nif (m != null)
\n{
\nConsole.WriteLine(m.ToString());
\n}
\nelse
\n{
\nConsole.WriteLine(“{0} is not a Mammal”, o.GetType().Name);
\n}
\n}<\/p>\n
void UseAsWithNullable(System.ValueType val)
\n{
\nint? j = val as\u00a0int?;
\nif (j != null)
\n{
\nConsole.WriteLine(j);
\n}
\nelse
\n{
\nConsole.WriteLine(“Could not convert ” + val.ToString());
\n}
\n}
\n}<\/p>\n","protected":false},"excerpt":{"rendered":"
The\u00a0as operator is more efficient because it actually returns the cast value if the cast can be made successfully. The is operator returns only a Boolean value. It can therefore be used when we just want to determine an object’s type but do not have to actually cast it. Use the is operator to verify the type before performing a… Read more →<\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-132","post","type-post","status-publish","format-standard","hentry","category-c-vb","xfolkentry"],"_links":{"self":[{"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/132","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=132"}],"version-history":[{"count":0,"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=\/wp\/v2\/posts\/132\/revisions"}],"wp:attachment":[{"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=132"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=132"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/mairwa.com\/wordpress\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=132"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}