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  • C# Convert string to nullable type (int, double, etc...)

    - by Nathan Koop
    I am attempting to do some data conversion. Unfortunately, much of the data is in strings, where it should be int's or double, etc... So what I've got is something like: double? amount = Convert.ToDouble(strAmount); The problem with this approach is if strAmount is empty, if it's empty I want it to amount to be null, so when I add it into the database the column will be null. So I ended up writing this: double? amount = null; if(strAmount.Trim().Length>0) { amount = Convert.ToDouble(strAmount); } Now this works fine, but I now have five lines of code instead of one. This makes things a little more difficult to read, especially when I have a large amount of columns to convert. I thought I'd use an extension to the string class and generic's to pass in the type, this is because it could be a double, or an int, or a long. So I tried this: public static class GenericExtension { public static Nullable<T> ConvertToNullable<T>(this string s, T type) where T: struct { if (s.Trim().Length > 0) { return (Nullable<T>)s; } return null; } } But I get the error: Cannot convert type 'string' to 'T?' Is there a way around this? I am not very familiar with creating methods using generics.

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  • C# Access the Properties of a Generic Object

    - by Jimbo
    I have a method that counts the number of Contacts each Supplier, Customer and Manufacturer has (this is a scenario to try make explaining easier!) The models are all created by Linq to SQL classes. Each Supplier, Customer and Manufacturer may have one or more Contacts public int CountContacts<TModel>(TModel entity) where TModel : class { return entity.Contacts.Count(); } The above of course doesnt work, because the 'entity' is generic and doesnt know whether it has the property 'Contacts'. Can someone help with how to achieve this?

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  • What is the difference in WCF when using KnownType and ServiceKnownType?

    - by Paul Speranza
    I have a service that returns an array of animal but the list can contain cats, dogs, etc, which all extend animal. I know I need to use either the KnownType or ServiceKnownType attribute, and on the entity class or the service class, respectively. What is the difference between the 2 attributes? I prefer the ServiceKnownType because it is applied on the service, exactly where it is needed and called for, as opposed to KnownType which is applied on my entity. To me applying it on the entity class means knowing too far ahead how my entity class is being used. For now I have it on my entity and it works like a charm, but I am looking for guidance here as to best practices and usefullness. Thanks, Paul Speranza

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  • How can I access the group of a linq group-by query from a nested repeater control?

    - by Duke
    I'm using a linq group by query (with two grouping parameters) and would like to use the resulting data in a nested repeater. var dateGroups = from row in data.AsEnumerable() group row by new { StartDate = row["StartDate"], EndDate = row["EndDate"] }; "data" is a DataTable from an SqlDataAdapter-filled DataSet. "dateGroups" is used in the parent repeater, and I can access the group keys using Eval("key.StartDate") and Eval("key.EndDate"). Since dateGroups actually contains all the data rows grouped neatly by Start/End date, I'd like to access those rows to display the data in a child repeater. To what would I set the child repeater's DataSource? I have tried every expression in markup I could think of; I think the problem is that I'm trying to access an anonymous member (and I don't know how.) In case it doesn't turn out to be obvious, what would be the expression to access the elements in each iteration of the child repeater? Is there an expression that would let me set the DataSource in the markup, or will it have to be in the codebehind on some event in the parent repeater?

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  • linq2sql : get generic type of table

    - by benpage
    i think this is a simple question but I've searched around and can't seem to find an answer easily. if you have var list = List<int>(); ... fill list ... and you want to get the generic type in list, i realise you could just type: var t = list.FirstOrDefault().GetType(); Is there another way to do this via just the list, rather than referring to the enumeration? Reason is, i have a System.Data.Linq.Table<TABLE1> and what i want to do is get the type of TABLE1 from it. so: var table = new DataContext().TABLE1s; // this is Table<TABLE1> var tableType = table.GetType().SomeMethod(); // i want tableType to equal TABLE1.GetType()

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  • Solving a difficult incomplete type error

    - by ChAoS
    I get an incomplete type error when trying to compile my code. I know that it is related to includes, but my project is large and it uses several templates so I can't find which type is actually incomplete. The error message doesn't help either: Compiling: ../../../addons/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp In file included from ../../../addons/ofxTableGestures/ext/boost/fusion/include/invoke_procedure.hpp:10, from ../../../addons/ofxTableGestures/src/oscGestures/tuioApp.hpp:46, from /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.hpp:35, from /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp:31: ../../../addons/ofxTableGestures/ext/boost/fusion/functional/invocation/invoke_procedure.hpp: In function ‘void boost::fusion::invoke_procedure(Function, const Sequence&) [with Function = void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), Sequence = boost::fusion::joint_view<boost::fusion::joint_view<boost::fusion::iterator_range<boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0> >, const boost::fusion::single_view<tuio::CanBasicFingers<Graphic>*> >, boost::fusion::iterator_range<boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 6> > >]’: ../../../addons/ofxTableGestures/src/oscGestures/tuioApp.hpp:122: instantiated from ‘void tuio::AlternateCallback<C, M, E>::run(tuio::TEvent*) [with C = tuio::CanBasicFingers<Graphic>, M = void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), E = tuio::TeventBasicFingersMoveFinger]’ /home/thechaos/Projectes/of_preRelease_v0061_linux_FAT/addons/../apps/OF-TangibleFramework/ofxTableGestures/src/Graphics/objects/CursorFeedback.cpp:64: instantiated from here ../../../addons/ofxTableGestures/ext/boost/fusion/functional/invocation/invoke_procedure.hpp:88: error: incomplete type ‘boost::fusion::detail::invoke_procedure_impl<void (tuio::CanBasicFingers<Graphic>::*)(long int, float, float, float, float, float), const boost::fusion::joint_view<boost::fusion::joint_view<boost::fusion::iterator_range<boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0> >, const boost::fusion::single_view<tuio::CanBasicFingers<Graphic>*> >, boost::fusion::iterator_range<boost::fusion::vector_iterator<boost::fusion::vector6<long int, float, float, float, float, float>, 0>, boost::fusion::vector_iterator<const boost::fusion::vector6<long int, float, float, float, float, float>, 6> > >, 7, true, false>’ used in nested name specifier If I copy the conflictive code to a same file I can compile it. So I know that the code itself is OK, the problem is the way I instantiate it. How can I trace the origin of this error? Is there any way to get the trace of the c++ compiler and preprocessor to get more informative messages?

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  • Objective-C : BOOL vs bool

    - by santoni
    Hi, I'm new to objective-c and I saw the "new type" BOOL (YES, NO). I read that this type is almost like a char. For testing I did : NSLog(@"Size of BOOL %d", sizeof(BOOL)); NSLog(@"Size of bool %d", sizeof(bool)); Good to see both display 1 (sometimes in C++ bool just an int and sizeof is 4) So I was just wondering I there were some issues with the bool type or something ? Can I just use bool (that seems to work) without loosing speed? Thanks for answers

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  • How do I iterate over the properties of an anonymous object in C#?

    - by Tomas Lycken
    I want to take an anonymous object as argument to a method, and then iterate over its properties to add each property/value to a a dynamic ExpandoObject. So what I need is to go from new { Prop1 = "first value", Prop2 = SomeObjectInstance, Prop3 = 1234 } to knowing names and values of each property, and being able to add them to the ExpandoObject. How do I accomplish this? Side note: This will be done in many of my unit tests (I'm using it to refactor away a lot of junk in the setup), so performance is to some extent relevant. I don't know enough about reflection to say for sure, but from what I've understood it's pretty performance heavy, so if it's possible I'd rather avoid it... Follow-up question: As I said, I'm taking this anonymous object as an argument to a method. What datatype should I use in the method's signature? Will all properties be available if I use object?

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  • PLPGSQL array assignment not working, "array subscript in assignment must not be null"

    - by Koen Schmeets
    Hello there, When assigning mobilenumbers to a varchar[] in a loop through results it gives me the following error: "array subscript in assignment must not be null" Also, i think the query that joins member uuids, and group member uuids, into one, grouped on the user_id, i think it can be done better, or maybe this is even why it is going wrong in the first place! Any help is very appreciated.. Thank you very much! CREATE OR REPLACE FUNCTION create_membermessage(in_company_uuid uuid, in_user_uuid uuid, in_destinationmemberuuids uuid[], in_destinationgroupuuids uuid[], in_title character varying, in_messagecontents character varying, in_timedelta interval, in_messagecosts numeric, OUT out_status integer, OUT out_status_description character varying, OUT out_value VARCHAR[], OUT out_trigger uuid[]) RETURNS record LANGUAGE plpgsql AS $$ DECLARE temp_count INTEGER; temp_costs NUMERIC; temp_balance NUMERIC; temp_campaign_uuid UUID; temp_record RECORD; temp_mobilenumbers VARCHAR[]; temp_destination_uuids UUID[]; temp_iterator INTEGER; BEGIN out_status := NULL; out_status_description := NULL; out_value := NULL; out_trigger := NULL; SELECT INTO temp_count COUNT(*) FROM costs WHERE costtype = 'MEMBERMESSAGE' AND company_uuid = in_company_uuid AND startdatetime < NOW() AND (enddatetime > NOW() OR enddatetime IS NULL); IF temp_count > 1 THEN out_status := 1; out_status_description := 'Invalid rows in costs table!'; RETURN; ELSEIF temp_count = 1 THEN SELECT INTO temp_costs costs FROM costs WHERE costtype = 'MEMBERMESSAGE' AND company_uuid = in_company_uuid AND startdatetime < NOW() AND (enddatetime > NOW() OR enddatetime IS NULL); ELSE SELECT INTO temp_costs costs FROM costs WHERE costtype = 'MEMBERMESSAGE' AND company_uuid IS NULL AND startdatetime < NOW() AND (enddatetime > NOW() OR enddatetime IS NULL); END IF; IF temp_costs != in_messagecosts THEN out_status := 2; out_status_description := 'Message costs have changed during sending of the message'; RETURN; ELSE SELECT INTO temp_balance balance FROM companies WHERE company_uuid = in_company_uuid; SELECT INTO temp_count COUNT(*) FROM users WHERE (user_uuid = ANY(in_destinationmemberuuids)) OR (user_uuid IN (SELECT user_uuid FROM targetgroupusers WHERE targetgroup_uuid = ANY(in_destinationgroupuuids)) ) GROUP BY user_uuid; temp_campaign_uuid := generate_uuid('campaigns', 'campaign_uuid'); INSERT INTO campaigns (company_uuid, campaign_uuid, title, senddatetime, startdatetime, enddatetime, messagetype, state, message) VALUES (in_company_uuid, temp_campaign_uuid, in_title, NOW() + in_timedelta, NOW() + in_timedelta, NOW() + in_timedelta, 'MEMBERMESSAGE', 'DRAFT', in_messagecontents); IF in_timedelta > '00:00:00' THEN ELSE IF temp_balance < (temp_costs * temp_count) THEN UPDATE campaigns SET state = 'INACTIVE' WHERE campaign_uuid = temp_campaign_uuid; out_status := 2; out_status_description := 'Insufficient balance'; RETURN; ELSE UPDATE campaigns SET state = 'ACTIVE' WHERE campaign_uuid = temp_campaign_uuid; UPDATE companies SET balance = (temp_balance - (temp_costs * temp_count)) WHERE company_uuid = in_company_uuid; SELECT INTO temp_destination_uuids array_agg(DISTINCT(user_uuid)) FROM users WHERE (user_uuid = ANY(in_destinationmemberuuids)) OR (user_uuid IN(SELECT user_uuid FROM targetgroupusers WHERE targetgroup_uuid = ANY(in_destinationgroupuuids))); RAISE NOTICE 'Array is %', temp_destination_uuids; FOR temp_record IN (SELECT u.firstname, m.mobilenumber FROM users AS u LEFT JOIN mobilenumbers AS m ON m.user_uuid = u.user_uuid WHERE u.user_uuid = ANY(temp_destination_uuids)) LOOP IF temp_record.mobilenumber IS NOT NULL AND temp_record.mobilenumber != '' THEN --THIS IS WHERE IT GOES WRONG temp_mobilenumbers[temp_iterator] := ARRAY[temp_record.firstname::VARCHAR, temp_record.mobilenumber::VARCHAR]; temp_iterator := temp_iterator + 1; END IF; END LOOP; out_status := 0; out_status_description := 'Message created successfully'; out_value := temp_mobilenumbers; RETURN; END IF; END IF; END IF; END$$;

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  • Double type returns -1.#IND/NaN error when calculating pi iteratively

    - by Draak
    I am working through a problem for my MCTS certification. The program has to calculate pi until the user presses a key, at which point the thread is aborted, the result returned to the main thread and printed in the console. Simple enough, right? This exercise is really meant to be about threading, but I'm running into another problem. The procedure that calculates pi returns -1.#IND. I've read some of the material on the web about this error, but I'm still not sure how to fix it. When I change double to Decimal type, I unsurprisingly get Overflow Exception very quickly. So, the question is how do I store the numbers correctly? Do I have to create a class to somehow store parts of the number when it gets too big to be contained in a Decimal? Class PiCalculator Dim a As Double = 1 Dim b As Double = 1 / Math.Sqrt(2) Dim t As Double = 1 / 4 Dim p As Double = 1 Dim pi As Double Dim callback As DelegateResult Sub New(ByVal _callback As DelegateResult) callback = _callback End Sub Sub Calculate() Try Do While True Dim a1 = (a + b) / 2 Dim b1 = Math.Sqrt(a * b) Dim t1 = t - p * (a - a1) ^ 2 Dim p1 = 2 * p a = a1 b = b1 t = t1 p = p1 pi = ((a + b) ^ 2) / (4 * t) Loop Catch ex As ThreadAbortException Finally callback(pi) End Try End Sub End Class

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  • Java - short and casting

    - by chr1s
    Hi all, I have the following code snippet. public static void main(String[] args) { short a = 4; short b = 5; short c = 5 + 4; short d = a; short e = a + b; // does not compile (expression treated as int) short z = 32767; short z_ = 32768; // does not compile (out of range) test(a); test(7); // does not compile (not applicable for arg int) } public static void test(short x) { } Is the following summary correct (with regard to only the example above using short)? direct initializations without casting is only possible using literals or single variables (as long as the value is in the range of the declared type) if the rhs of an assignment deals with expressions using variables, casting is necessary But why exactly do I need to cast the argument of the second method call taking into account the previous summary?

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  • Possible to create an implicit cast for an anonymous type to a dictionary?

    - by Ralph
    I wrote a method like this: using AttrDict = System.Collections.Generic.Dictionary<string, object>; using IAttrDict = System.Collections.Generic.IEnumerable<System.Collections.Generic.KeyValuePair<string, object>>; static string HtmlTag(string tagName, string content = null, IAttrDict attrs = null) { var sb = new StringBuilder("<"); sb.Append(tagName); if(attrs != null) foreach (var attr in attrs) sb.AppendFormat(" {0}=\"{1}\"", attr.Key, attr.Value.ToString().EscapeQuotes()); if (content != null) sb.AppendFormat(">{0}</{1}>", content, tagName); else sb.Append(" />"); return sb.ToString(); } Which you can call like HtmlTag("div", "hello world", new AttrDict{{"class","green"}}); Not too bad. But what if I wanted to allow users to pass an anonymous type in place of the dict? Like HtmlTag("div", "hello world", new {@class="green"}); Even better! I could write the overload easily, but the problem is I'm going to have about 50 functions like this, I don't want to overload each one of them. I was hoping I could just write an implicit cast to do the work for me... public class AttrDict : Dictionary<string, object> { public static implicit operator AttrDict(object obj) { // conversion from anonymous type to AttrDict here } } But C# simply won't allow it: user-defined conversions to or from a base class are not allowed So what can I do?

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  • Accessing C# Anonymous Type Objects

    - by Ali Kazmi
    Hi, How do i access objects of an anonymous type outside the scope where its declared? for e.g. void FuncB() { var obj = FuncA(); Console.WriteLine(obj.Name); } ??? FuncA() { var a = (from e in DB.Entities where e.Id == 1 select new {Id = e.Id, Name = e.Name}).FirstOrDefault(); return a; }

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  • Who likes short shorts?

    - by kiwicptn
    I got $2 change instead of $3 today and that got me thinking about short for some reason. What can do (these days ;-p) with a variable of the short primitive type (16 bits signed)? Any good reason to keep them around?

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  • .NET Type Conversion Issue: Simple but difficult

    - by jaderanderson
    Well, the question is kinda simple. I have a object defined as: public class FullListObject : System.Collections.ArrayList, IPagedCollection And when i try to: IPagedCollection pagedCollection = (IPagedCollection)value; It don't work... value is a FullListObject... this is my new code trying to get around a issue with the "is" operator. When the system tests (value is IPagedCollection) it never gets true for FullListObject. How to cast the object to another object with a interface type?

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  • Rails: creating a custom data type / creating a shorthand

    - by Shyam
    Hi, I am wondering how I could create a custom data type to use within the rake migration file. Example: if you would be creating a model, inside the migration file you can add columns. It could look like this: def self.up create_table :products do |t| t.column :name, :string t.timestamps end end I would like to know how to create something like this: t.column :name, :my_custom_data_type The reason for this to create for example a "currency" type, which is nothing more than a decimal with a precision of 8 and a scale of 2. Since I use only MySQL, the solution for this database is sufficient enough. Thank you for your feedback and comments!

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  • Variadic templates in Scala

    - by Thomas Jung
    Suppose you want to have something like variadic templates (the ability to define n type parameters for a generic class) in Scala. For example you do not want to define Tuple2[+T1, +T2] and Tuple3[+T1, +T2, +T3] but Tuple[T*]. Are there other options than HLists?

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  • pointer reference type

    - by Codenotguru
    I am trying to write a function that takes a pointer argument, modifies what the pointer points to, and then returns the destination of the pointer as a reference. I am gettin the following error: cannot convert int***' toint*' in return| Code: #include <iostream> using namespace std; int* increment(int** i) { i++; return &i;} int main() { int a=24; int *p=&a; int *p2; p2=increment(&p); cout<<p2; } Thanks for helping!

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