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  • Design Patterns: What is a type

    - by contactmatt
    A very basic question, but after reading the "Design Patterns: Elements of reusable OO Software" book, I'm a little confused. The book states, "An object's type only refers to its interface-the set of request to which it can respond. An object can have many types, and objects of different classes can have the same type." Could someone please better explain what a Type is? I also don't understand how one object can have multiple types...unless the book is speaking of polymorphism....

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  • Suppress Null Value Types from Being Emitted by XmlSerializer

    - by Ben Griswold
    Please consider the following Amount value type property which is marked as a nullable XmlElement: [XmlElement(IsNullable=true)] public double? Amount { get ; set ; } When a nullable value type is set to null, the C# XmlSerializer result looks like the following: <amount xsi:nil="true" /> Rather than emitting this element, I would like the XmlSerializer to suppress the element completely. Why? We're using Authorize.NET for online payments and Authorize.NET rejects the request if this null element exists. The current solution/workaround is to not serialize the Amount value type property at all. Instead we have created a complementary property, SerializableAmount, which is based on Amount and is serialized instead. Since SerializableAmount is of type String, which like reference types are suppressed by the XmlSerializer if null by default, everything works great. /// <summary> /// Gets or sets the amount. /// </summary> [XmlIgnore] public double? Amount { get; set; } /// <summary> /// Gets or sets the amount for serialization purposes only. /// This had to be done because setting value types to null /// does not prevent them from being included when a class /// is being serialized. When a nullable value type is set /// to null, such as with the Amount property, the result /// looks like: &gt;amount xsi:nil="true" /&lt; which will /// cause the Authorize.NET to reject the request. Strings /// when set to null will be removed as they are a /// reference type. /// </summary> [XmlElement("amount", IsNullable = false)] public string SerializableAmount { get { return this.Amount == null ? null : this.Amount.ToString(); } set { this.Amount = Convert.ToDouble(value); } } Of course, this is just a workaround. Is there a cleaner way to suppress null value type elements from being emitted?

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  • Getting types of the attributes in an ActiveRecord object

    - by Michael Neale
    I would like to know if it is possible to get the types (as known by AR - eg in the migration script and database) programmatically (I know the data exists in there somewhere). For example, I can deal with all the attribute names: ar.attribute_names.each { |name| puts name } .attributes just returns a mapping of the names to their current values (eg no type info if the field isn't set). Some places I have seen it with the type information: in script/console, type the name of an AR entity: >> Driver => Driver(id: integer, name: string, created_at: datetime, updated_at: datetime) So clearly it knows the types. Also, there is .column_for_attribute, which takes an attr name and returns a column object - which has the type buried in the underlying database column object, but it doesn't appear to be a clean way to get it. I would also be interested in if there is a way that is friendly for the new "ActiveModel" that is coming (rails3) and is decoupled from database specifics (but perhaps type info will not be part of it, I can't seem to find out if it is). Thanks.

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  • QFileDialog filter from mime-types

    - by Mathias
    I want the filter in a QFileDialog to match all audio file types supported by Phonon on the platform in question. 1 - However I am not able to find a way in Qt to use mime types in a filter. How can I do that? 2 - Or how can I find the corresponding file extensions for the mimetypes manually? The solution should be Qt based, or at least be cross platform and supported everywhere Qt is. Following is a short code describing my problem: #include <QApplication> #include <QFileDialog> #include <QStringList> #include <phonon/backendcapabilities.h> QString mime_to_ext(QString mime) { // WHAT TO REALLY DO ?? // NEEDLESS TO SAY; THIS IS WRONG... return mime.split("/").back().split('-').back(); } int main(int argc, char **argv) { QApplication app(argc, argv); QStringList p_audio_exts; QStringList p_mime_types = Phonon::BackendCapabilities::availableMimeTypes(); for(QStringList::iterator i = p_mime_types.begin(), ie = p_mime_types.end(); i != ie; i++) { if((*i).startsWith("audio")) p_audio_exts << mime_to_ext(*i); } QString filter = QString("All Files(*)"); if(!p_audio_exts.isEmpty()) { QString p_audio_filter = QString("Audio Files (*.%1)").arg(p_audio_exts.join(" *.")); filter = QString("%1;;%2").arg(p_audio_filter).arg(filter); } QFileDialog dialog(NULL, "Open Audio File", QString::null, filter); dialog.exec(); }

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  • Optimal Serialization of Primitive Types

    - by Greg Dean
    We are beginning to roll out more and more WAN deployments of our product (.Net fat client w/ IIS hosted Remoting backend). Because of this we are trying to reduce the size of the data on the wire. We have overridden the default serialization by implementing ISerializable (similar to this), we are seeing anywhere from 12% to 50% gains. Most of our efforts focus on optimizing arrays of primitive types. I would like to know if anyone knows of any fancy way of serializing primitive types, beyond the obvious? For example today we serialize an array of ints as follows: [4-bytes (array length)][4-bytes][4-bytes] Can anyone do significantly better? The most obvious example of a significant improvement, for boolean arrays, is putting 8 bools in each byte, which we already do. Note: Saving 7 bits per bool may seem like a waste of time, but when you are dealing with large magnitudes of data (which we are), it adds up very fast. Note: We want to avoid general compression algorithms because of the latency associated with it. Remoting only supports buffered requests/responses(no chunked encoding). I realize there is a fine line between compression and optimal serialization, but our tests indicate we can afford very specific serialization optimizations at very little cost in latency. Whereas reprocessing the entire buffered response into new compressed buffer is too expensive.

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  • CreateDelegate with unknown types

    - by Giorgi
    Hello, I am trying to create Delegate for reading/writing properties of unknown type of class at runtime. I have a generic class Main<T> and a method which looks like this: Delegate.CreateDelegate(typeof(Func<T, object>), get) where get is a MethodInfo of the property that should be read. The problem is that when the property returns int (I guess this happens for value types) the above code throws ArgumentException because the method cannot be bound. In case of string it works well. To solve the problem I changed the code so that corresponding Delegate type is generated by using MakeGenericType. So now the code is: Type func = typeof(Func<,>); Type generic = func.MakeGenericType(typeof(T), get.ReturnType); var result = Delegate.CreateDelegate(generic, get) The problem now is that the created delegate instance of generic so I have to use DynamicInvoke which would be as slow as using pure reflection to read the field. So my question is why is that the first snippet of code fails with value types. According to MSDN it should work as it says that The return type of a delegate is compatible with the return type of a method if the return type of the method is more restrictive than the return type of the delegate and how to execute the delegate in the second snippet so that it is faster than reflection. Thanks.

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  • How to record different authentication types (username / password vs token based) in audit log

    - by RM
    I have two types of users for my system, normal human users with a username / password, and delegation authorized accounts through OAuth (i.e. using a token identifier). The information that is stored for each is quite different, and are managed by different subsytems. They do however interact with the same tables / data within the system, so I need to maintain the audit trail regardless of whether human user, or token-based user modified the data. My solution at the moment is to have a table called something like AuditableIdentity, and then have the two types inheriting off that table (either in the single table, or as two seperate tables with 1 to 1 PK with AuditableIdentity. All operations would use the common AuditableIdentity PK for CreatedBy, ModifiedBy etc columns. There isn't any FK constraint on the audit columns, so any text can go in there, but I want an easy way to easily determine whether it was a human or system that made the change, and joining to the one AuditableIdentity table seems like a clean way to do that? Is there a best practice for this scenario? Is this an appropriate way of approaching the problem - or would you not bother with the common table and just rely on joins (to the two seperate un-related user / token tables) later to determine which user type matches which audit records?

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  • c incompatible types in assignment, problem with pointers?

    - by Fantastic Fourier
    Hi I'm working with C and I have a question about assigning pointers. struct foo { int _bar; char * _car[MAXINT]; // this is meant to be an array of char * so that it can hold pointers to names of cars } int foofunc (void * arg) { int bar; char * car[MAXINT]; struct foo thing = (struct foo *) arg; bar = arg->_bar; // this works fine car = arg->_car; // this gives compiler errors of incompatible types in assignment } car and _car have same declaration so why am I getting an error about incompatible types? My guess is that it has something to do with them being pointers (because they are pointers to arrays of char *, right?) but I don't see why that is a problem. when i declared char * car; instead of char * car[MAXINT]; it compiles fine. but I don't see how that would be useful to me later when I need to access certain info using index, it would be very annoying to access that info later. in fact, I'm not even sure if I am going about the right way, maybe there is a better way to store a bunch of strings instead of using array of char *?

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  • Incompatible types when assigning to type 'struct compartido'

    - by user1660559
    I have one problem with this code. I should create one structure and share it across 5 new process created from the father: #include <stdio.h> #include <stdlib.h> #include <sys/wait.h> #include <unistd.h> #include <sys/types.h> #include <sys/ipc.h> #include <sys/shm.h> #include <sys/sem.h> #include <time.h> struct compartido { int pid1, pid2, pid3, pid4, pid5; int propietario; int contador; int pidpadre; }; struct compartido var; int main(int argc, char *argv[]) { key_t llave1,llavesem; int idmem,idsem; llave1=ftok("/tmp",'a'); idmem=shmget(llave1,sizeof(int),IPC_CREAT|0600); if (idmem==-1) { perror ("shmget"); return 1; } var=shmat(idmem,0,0); /*This line is giving the error*/ /*rest of the code*/ } The exact error is giving is: error: incompatible types when assigning to type 'struct compartido' from type 'void *' I need to put this structure in the shared variable to be able to see and modify all those data from the 6 process (5 children and the father). What I'm doing bad? Thanks in advance and best regards,

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  • C: incompatible types in assignment

    - by The.Anti.9
    I'm writing a program to check to see if a port is open in C. One line in particular copies one of the arguments to a char array. However, when I try to compile, it says: error: incompatible types in assignment Heres the code. The error is on the assignment of addr #include <sys/socket.h> #include <sys/time.h> #include <sys/types.h> #include <arpa/inet.h> #include <netinet/in.h> #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <netdb.h> #include <stdlib.h> #include <string.h> #include <unistd.h> int main(int argc, char **argv) { u_short port; /* user specified port number */ char addr[1023]; /* will be a copy of the address entered by u */ struct sockaddr_in address; /* the libc network address data structure */ short int sock = -1; /* file descriptor for the network socket */ port = atoi(argv[1]); addr = strncpy(addr, argv[2], 1023); bzero((char *)&address, sizeof(address)); /* init addr struct */ address.sin_addr.s_addr = inet_addr(addr); /* assign the address */ address.sin_port = htons(port); /* translate int2port num */ sock = socket(AF_INET, SOCK_STREAM, 0); if (connect(sock,(struct sockaddr *)&address,sizeof(address)) == 0) { printf("%i is open\n", port); } if (errno == 113) { fprintf(stderr, "Port not open!\n"); } close(sock); return 0; } I'm new to C, so I'm not sure why it would do this.

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  • Namespace scoped aliases for generic types in C#

    - by TN
    Let's have a following example: public class X { } public class Y { } public class Z { } public delegate IDictionary<Y, IList<Z>> Bar(IList<X> x, int i); public interface IFoo { // ... Bar Bar { get; } } public class Foo : IFoo { // ... public Bar Bar { get { return null; //... } } } void Main() { IFoo foo; //= ... IEnumerable<IList<X>> source; //= ... var results = source.Select(foo.Bar); } The compiler says: The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. It's because, it cannot convert Bar to Func<IList<X>, int, IDictionary<Y, IList<Z>>>. It would be great if I could create type namespace scoped type aliases for generic types in C#. Then I would define Bar not as a delegate, but rather I would define it as an namespace scoped alias for Func<IList<X>, int, IDictionary<Y, IList<Z>>>. public alias Bar = Func<IList<X>, int, IDictionary<Y, IList<Z>>>; I could then also define namespace scoped alias for e.g. IDictionary<Y, IList<Z>>. And if used appropriately:), it will make the code more readable. Now I have inline the generic types and the real code is not well readable:( Have you find the same trouble:)? Is there any good reason why it is not in C# 3.0? Or there is no good reason, it's just matter of money and/or time? EDIT: I know that I can use using, but it is not namespace based - not so convenient for my case.

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  • Using delegate Types vs methods

    - by Grant Sutcliffe
    I see increasing use of the delegate types offered in the System namespace (Action; Predicate etc). As these are delegates, my understanding is that they should be used where we have traditionally used delegates in the past (asynchronous calls; starting threads, event handling etc). Is it just preference or is it considered practice to use these delegate types in scenarios such as the below; rather than using calls to methods we have declared (or anonymous methods): public void MyMethod { Action<string> action = delegate(string userName { try { XmlDocument profile = DataHelper.GetProfile(userName); UpdateMember(profile); } catch (Exception exception) { if (_log.IsErrorEnabled) _log.ErrorFormat(exception.Message); throw (exception); } }; GetUsers().ForEach(action); } At first, I found the code less intuitive to follow than using declared or anonymous methods. I am starting to code this way, and wonder what the view are in this regard. The example above is all within a method. Is this delegate overuse.

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  • C++ Design Question on template types

    - by user231536
    I have a templated class template <typename T> class MyContainerClass For types to be substituted for T, it has to satisfy many requirements: for example, get_id(), int data(), etc. Obviously none of the fundamental types (PODs) are substitutable. One way I can provide this is via wrappers for the PODs that provide these functions. Is this an acceptable way? Another way would be to change the template to: template < typename T, typename C=traits<T> > class MyContainerClass and inside MyContainerClass, call traits::data() instead of data() on T objects. I will specialize traits<int>, traits<const char *> etc. Is this good design ? How do I design such a traits class (completely static methods or allow for inheritance) ? Or are the wrapper classes a good solution? What other alternatives are there?

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  • Container of Generic Types in java

    - by Cyker
    I have a generic class Foo<T> and parameterized types Foo<String> and Foo<Integer>. Now I want to put different parameterized types into a single ArrayList. What is the correct way of doing this? Candidate 1: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo<?> > list = new ArrayList<Foo<?> >(); list.add(fooString); list.add(fooInteger); for (Foo<?> foo : list) { // Do something on foo. } } } class Foo<T> {} Candidate 2: public class MMM { public static void main(String[] args) { Foo<String> fooString = new Foo<String>(); Foo<Integer> fooInteger = new Foo<Integer>(); ArrayList<Foo> list = new ArrayList<Foo>(); list.add(fooString); list.add(fooInteger); for (Foo foo : list) { // Do something on foo. } } } class Foo<T> {} In a word, it is related to the difference between Foo<?> and the raw type Foo. Update: Grep What is the difference between the unbounded wildcard parameterized type and the raw type? on this link may be helpful.

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  • Which book for windows Shell programming?

    - by serefarikan
    I've been looking for a good book for windows shell programming, and the only one I could find is Visual C++ Windows Shell Programming by Dino Eposito: http://www.wintellect.com/BookInformation.aspx?ASIN=1861001843 It is an old book, and I'd like to know if you know of any good resources which could help. I need to develop a couple of windows explorer extensions, and apparently managed code is not recommended by Microsoft at least for some of these tasks. So I'm searching for a good resource for native development. Kind regards Seref

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  • jad for blackberry non-midlet application

    - by Durgesh
    Hi Experts, I am writing a regular application for Blackberry. I want to know, is there anything similiar to JAD for pure native blackberry application (no j2me) ? If JAD is applicable to regular BB app then please guide me to use JAD for it. Kind Regards -Durgesh O Mishra

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  • Problem initialing a unicode string

    - by Simon
    Hey All. Atm im working with native API calls and i have to get RtlInitUnicodeString to work. The way i use: const WCHAR wcMutex[] = L"String1"; UNICODE_STRING unicodeMutexBuffer; RtlInitUnicodeString(&unicodeMutexBuffer,wcMutex); now my problem the project doesnt compile , i get this error: Error argument of type "UNICODE_STRING*" is incompatible with type of "PUNICODE_STRING" but in my old Driver kit , i used same way to initialize the unicode string struct

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  • How to load jni from sd card on android 2.1?

    - by user263423
    I want to load third-party jni library in runtime. I've tried to load directly from sdcard. It expectedly failed. I've tried to copy library from sdcard to /data/data/app/ and then System.load(/data/data/libjni.so) It works on HTC HERO, but fails on HTC Legend with Android 2.1. it fails during execution of native code and write to log uninformative stack trace Any other way to do it?

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  • What stops HTML5 and JS apps to perform as good as native apps?

    - by Amogh Talpallikar
    From what I understand, HTML is a mark-up language, so is the content of XAML, XIB and whatever Android uses and other native UI development frameworks. JavaScript is a programming language used along with it to handle client side scripting which will include things like event handling, client side validations and anything else C#,Java,Objective-C or C++ do in various such frameworks. There are MVC/MVVM patterns available in form frameworks like Sencha's, Angular etc. We have localStorage in form of both sqlite and key-value store as other frameworks have and you have API specification for almost everything that it missing. Whenever a native UI frameworks has to render UI , it has to parse a similar the markup and render the UI. Question break-down What stops from doing the same in HTML and JS itself ? Instead of having a web-control or browser as a layer in between why can't HTML(along with CSS) and JS be made to perform the same way ? Even if there is a layer,so does .net runtime and JVM are in other cases where C++,C are not being used. So Lets take the case of Android, like Dalvik, why Can't Chromium be another option(along with dalvik and NDK) where HTML does what android markup does and JavaScript is used to do what Java does ? So the Question is, Even if current implementations aren't as good, but theoretically is it possible to get HTML5 based applications to work as other native apps specially on mobile ?

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  • Server reporting incorrect mime type for css files

    - by Becky
    We have a VPS server that we host our websites on. I have written a CMS using CodeIgniter. On one of the interfaces, I am attempting to upload a css file to the system. This worked correctly when we had it hosted on shared hosting. Since we've moved it to the VPS, I am getting an "incorrect filetype" error. It all comes down to the fact that the server is reporting a mime type of text/x-c for the css file rather than text/css. I logged in via shell and ran the following command on an existing valid css file (to make sure it wasn't an issue with either CodeIgniter or with php). file --brief --mime 'filename.css' 2>&1 The server gave me the following in response to my command: text/x-c; charset=us-ascii My question ... is there some sort of server setting that I need to tweak to get the server to correctly identify the css file as text/css? Do I just have to add a mime type for the css files to the server? I found the mime types file (etc/mime.types), and it just hase video types and a couple other that I have no idea what they are. There is nothing in there for css or images or html files. Unless I'm looking in the wrong spot. I'm not a server person, so I'm hoping someone can help me out. Some server specs: Apache/2.2.22 (Unix) php 5.3.13 Server API = CGI/FastCGI the fileinfo php extension appears to be disabled

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  • Using stdint.h and ANSI printf?

    - by nn
    Hi, I'm writing a bignum library, and I want to use efficient data types to represent the digits. Particularly integer for the digit, and long (if strictly double the size of the integer) for intermediate representations when adding and multiplying. I will be using some C99 functionality, but trying to conform to ANSI C. Currently I have the following in my bignum library: #include <stdint.h> #if defined(__LP64__) || defined(__amd64) || defined(__x86_64) || defined(__amd64__) || defined(__amd64__) || defined(_LP64) typedef uint64_t u_w; typedef uint32_t u_hw; #define BIGNUM_DIGITS 2048 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT32_MAX #define U_HW_MIN UINT32_MIN #define U_W_MAX UINT64_MAX #define U_W_MIN UINT64_MIN #else typedef uint32_t u_w; typedef uint16_t u_hw; #define BIGNUM_DIGITS 4096 #define U_HW_BITS 16 #define U_W_BITS 32 #define U_HW_MAX UINT16_MAX #define U_HW_MIN UINT16_MIN #define U_W_MAX UINT32_MAX #define U_W_MIN UINT32_MIN #endif typedef struct bn { int sign; int n_digits; // #digits should exclude carry (digits = limbs) int carry; u_hw tab[BIGNUM_DIGITS]; } bn; As I haven't written a procedure to write the bignum in decimal, I have to analyze the intermediate array and printf the values of each digit. However I don't know which conversion specifier to use with printf. Preferably I would like to write to the terminal the digit encoded in hexadecimal. The underlying issue is, that I want two data types, one that is twice as long as the other, and further use them with printf using standard conversion specifiers. It would be ideal if int is 32bits and long is 64bits but I don't know how to guarantee this using a preprocessor, and when it comes time to use functions such as printf that solely rely on the standard types I no longer know what to use.

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  • Best way to databind a Winforms control to a nullable type?

    - by Steve Hiner
    I'm currently using winforms databinding to wire up a data editing form. I'm using the netTiers framework through CodeSmith to generate my data objects. For database fields that allow nulls it creates nullable types. I've found that using winforms databinding the controls won't bind properly to nullable types. I've seen solutions online suggesting that people create new textbox classes that can handle the nullable types but that could be a pain having to swap out the textboxes on the forms I've already created. Initially I thought it would be great to use an extension method to do it. Basically creating an extension property for the textbox class and bind to that. From my limited extension method experience and doing a bit of checking online it looks like you can't do an extension property. As far as I can tell, binding has to be through a property since it needs to be able to get or set the value so an extension method wouldn't work. I'd love to find a clean way to retrofit these forms using something like extension methods but if I have to create new textbox and combo box controls that's what I'll do. My project is currently limited to .Net 2.0 due to the requirement to run on Windows 2000. Any suggestions?

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  • Converting string to a simple type

    - by zespri
    .Net framework contains a great class named Convert that allows conversion between simple types, DateTime type and String type. Also the class support conversion of the types implementing IConvertible interface. The class has been implemented in the very first version of .Net framework. There were a few things in the first .Net framework that were not done quite right. For example .Parse methods on simple types would throw an exception if the string couldn't be parsed and there would be no way to check if exception is going to be thrown in advance. A future version of .Net Framework removed this deficiency by introducing the TryParse method that resolved this problem. The Convert class dates back to time of the old Parse method, so the ChangeType method on this class in implemented old style - if conversion can't be performed an exception is thrown. Take a look at the following code: public static T ConvertString<T>(string s, T @default) { try { return (T)Convert.ChangeType(s, typeof(T), CultureInfo.InvariantCulture); } catch (Exception) { return @default; } } This code basically does what I want. However I would pretty much like to avoid the ugly try/catch here. I'm sure, that similar to TryParse, there is a modern method of rewriting this code without the catch-all. Could you suggest one?

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  • PowerShell - Parameter Value Tab Expansion for Enum types

    - by Adam Driscoll
    Is it possible to implement parameter value tab expansion for enum parameter types? Creating a binary cmdlet with parameter definition: [Parameter] public SomeEnum Type {get;set;} Is there some way to type: Add-MyThing -Type S<tab> To get: Add-MyThing -Type SomeEnumValue Where: public enum SomeEnum { SomeEnumValue, SomeEnumValue2 } I know it may be possible with overriding the TabExpansion function but I was wondering if there was something I could do within my cmdlet to expose this type of functionality.

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