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  • Passing a LINQ DataRow Reference in a GridView's ItemTemplate

    - by Bob Kaufman
    Given the following GridView: <asp:GridView runat="server" ID="GridView1" AutoGenerateColumns="false" DataKeyNames="UniqueID" OnSelectedIndexChanging="GridView1_SelectedIndexChanging" > <Columns> <asp:BoundField HeaderText="Remarks" DataField="Remarks" /> <asp:TemplateField HeaderText="Listing"> <ItemTemplate> <%# ShowListingTitle( ( ( System.Data.DataRowView ) ( Container.DataItem ) ).Row ) %> </ItemTemplate> </asp:TemplateField> <asp:BoundField HeaderText="Amount" DataField="Amount" DataFormatString="{0:C}" /> </Columns> </asp:GridView> which refers to the following code-behind method: protected String ShowListingTitle( DataRow row ) { Listing listing = ( Listing ) row; return NicelyFormattedString( listing.field1, listing.field2, ... ); } The cast from DataRow to Listing is failing (cannot convert from DataRow to Listing) I'm certain the problem lies in what I'm passing from within the ItemTemplate, which is simply not the right reference to the current record from the LINQ to SQL data set that I've created, which looks like this: private void PopulateGrid() { using ( MyDataContext context = new MyDataContext() ) { IQueryable < Listing > listings = from l in context.Listings where l.AccountID == myAccountID select l; GridView1.DataSource = listings; GridView1.DataBind(); } }

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  • How to force ADO.Net to use only the System.String DataType in the readers TableSchema.

    - by Keith Sirmons
    Howdy, I am using an OleDbConnection to query an Excel 2007 Spreadsheet. I want force the OleDbDataReader to use only string as the column datatype. The system is looking at the first 8 rows of data and inferring the data type to be Double. The problem is that on row 9 I have a string in that column and the OleDbDataReader is returning a Null value since it could not be cast to a Double. I have used these connection strings: Provider=Microsoft.ACE.OLEDB.12.0;Data Source="ExcelFile.xlsx";Persist Security Info=False;Extended Properties="Excel 12.0;IMEX=1;HDR=No" Provider=Microsoft.Jet.OLEDB.4.0;Data Source="ExcelFile.xlsx";Persist Security Info=False;Extended Properties="Excel 8.0;HDR=No;IMEX=1" Looking at the reader.GetSchemaTable().Rows[7].ItemArray[5], it's dataType is Double. Row 7 in this schema correlates with the specific column in Excel I am having issues with. ItemArray[5] is its DataType column Is it possible to create a custom TableSchema for the reader so when accessing the ExcelFiles, I can treat all cells as text instead of letting the system attempt to infer the datatype? I found some good info at this page: Tips for reading Excel spreadsheets using ADO.NET The main quirk about the ADO.NET interface is how datatypes are handled. (You'll notice I've been carefully avoiding the question of which datatypes are returned when reading the spreadsheet.) Are you ready for this? ADO.NET scans the first 8 rows of data, and based on that guesses the datatype for each column. Then it attempts to coerce all data from that column to that datatype, returning NULL whenever the coercion fails! Thank you, Keith Here is a reduced version of my code: using (OleDbConnection connection = new OleDbConnection(BuildConnectionString(dataMapper).ToString())) { connection.Open(); using (OleDbCommand cmd = new OleDbCommand()) { cmd.Connection = connection; cmd.CommandText = SELECT * from [Sheet1$]; using (OleDbDataReader reader = cmd.ExecuteReader()) { using (DataTable dataTable = new DataTable("TestTable")) { dataTable.Load(reader); base.SourceDataSet.Tables.Add(dataTable); } } } }

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  • How to use Common Table Expression and check no duplication in SQL Server

    - by vodkhang
    I have a table references to itself. User table: id, username, managerid and managerid links back to id Now, I want to get all the managers including direct manager, manager of direct manager, so on and so forth... The problem is that I do not want to have a unstop recursive sql. So, I want to check if an id alreay in a list, I will not include it anymore. Here is my sql for that: with all_managers (id, username, managerid, idlist) as ( select u1.id, u1.username, u1.managerid, ' ' from users u1, users u2 where u1.id = u2.managerid and u2.id = 6 UNION ALL select u.id, u.username, u.managerid, idlist + ' ' + u.id from all_managers a, users u where a.managerid = u.id and charindex(cast(u.id as nvarchar(5)), idlist) != 0 ) select id, username from all_managers; The problem is that in this line: select u1.id, u1.username, u1.managerid, ' ' The SQL Server complains with me that I can not put ' ' as the initialized for idlist. nvarchar(40) does not work as well. I do not know how to declare it inside a common table expression like this one. Usually, in db2, I can just put varchar(40) My sample data: ID UserName ManagerID 1 admin 1 2 a 1 3 b 1 4 c 2 What I want to do is that I want to find all managers of c guy. The result should be: admin, a, b. Some of the user can be his manager (like admin) because the ManagerID does not allow NULL and some does not have direct manager. With common table expression, it can lead to an infinite recursive. So, I am also trying to avoid that situation by trying to not include the id twice. For example, in the 1st iteration, we already have id : 1, so, in the 2nd iteration and later on, 1 should never be allowed. I also want to ask if my current approach is good or not and any other solutions? Because if I have a big database with a deep hierarchy, I will have to initialize a big varchar to keep it and it consumes memory, right?

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  • Different location of assemblies stoped the type casting.

    - by smwikipedia
    I am writing a custom Control class in C# for my main project. There're 2 projects, one for my Control and one for my main project. These 2 projects are in the same solution. I add a reference from my main project to my Control project. I notice that the first time after I drag my Control from the Tool Panel onto my main winform, an assembly folder was generated at the C:\Users\XXX\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies, and the folder name is something like "jlebh-py01". The first build is always OK, but after I rebuild my Control class or whole solution, a new assembly folder will be generated at C:\Users\XXX\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies, and then problem arises, my Control fails to behave well because Visual Studio says that the two types "originates from different location". The error message is as below: [A]MyControl.TypeXXX cannot be cast to [B]MyControl.TypeXXX. Type A orginates from assemblyXXX at location 'C:\Users\XXX\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies\jlebh-py01\MyControl.dll' Type B originats from assemblyXXX at location 'C:\Users\XXX\AppData\Local\Microsoft\VisualStudio\9.0\ProjectAssemblies\ue4i-z3j01\MyControl.dll' If I reference the Control DLL directly instead of through project reference, or never rebuild the Control project after use my Control in the main project, things seem to be OK. Does anyone knows why? Is it the proper way to develop a control and a main project within the same solution? Many thanks...

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  • Why is XmlSerializer so hard to use?

    - by mafutrct
    I imagine to use XML serialization like this: class Foo { public Foo (string name) { Name1 = name; Name2 = name; } [XmlInclude] public string Name1 { get; private set; } [XmlInclude] private string Name2; } StreamWriter wr = new StreamWriter("path.xml"); new XmlSerializer<Foo>().Serialize (wr, new Foo ("me")); But this does not work at all: XmlSerializer is not generic. I have to cast from and to object on (de)serialization. Every property has to be fully public. Why aren't we just using Reflection to access private setters? Private fields cannot be serialized. I'd like to decorate private fields with an attribute to have XmlSerializer include them. Did I miss something and XmlSerializer is actually offering the described possibilities? Are there alternate serializers to XML that handle these cases more sophisticatedly? If not: We're in 2010 after all, and .NET has been around for many years. XML serialization is often used, totally standard and should be really easy to perform. Or is my understanding possibly wrong and XML serialization ought not to expose the described features for a good reason? (Feel free to adjust caption or tags. If this should be CW, please just drop a note.)

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  • Validating Application Settings Key Values in Isolated Storage for Windows Phone Applications

    - by Martin Anderson
    Hello everyone. I am very new at all this c# Windows Phone programming, so this is most probably a dumb question, but I need to know anywho... IsolatedStorageSettings appSettings = IsolatedStorageSettings.ApplicationSettings; if (!appSettings.Contains("isFirstRun")) { firstrunCheckBox.Opacity = 0.5; MessageBox.Show("isFirstRun not found - creating as true"); appSettings.Add("isFirstRun", "true"); appSettings.Save(); firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = true; } else { if (appSettings["isFirstRun"] == "true") { firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = true; } else if (appSettings["isFirstRun"] == "false") { firstrunCheckBox.Opacity = 1; firstrunCheckBox.IsChecked = false; } else { firstrunCheckBox.Opacity = 0.5; } } I am trying to firstly check if there is a specific key in my Application Settings Isolated Storage, and then wish to make a CheckBox appear checked or unchecked depending on if the value for that key is "true" or "false". Also I am defaulting the opacity of the checkbox to 0.5 opacity when no action is taken upon it. With the code I have, I get the warnings Possible unintended reference comparison; to get a value comparison, cast the left hand side to type 'string' Can someone tell me what I am doing wrong. I have explored storing data in an Isolated Storage txt file, and that worked, I am now trying Application Settings, and will finally try to download and store an xml file, as well as create and store user settings into an xml file. I want to try understand all the options open to me, and use which ever runs better and quicker

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  • Modifying a const through a non-const pointer

    - by jasonline
    I'm a bit confused what happened in the following code: const int e = 2; int* w = ( int* ) &e; // (1) cast to remove const-ness *w = 5; // (2) cout << *w << endl; // (3) outputs 5 cout << e << endl; // (4) outputs 2 cout << "w = " << w << endl; // (5) w points to the address of e cout << "&e = " << &e << endl; In (1), w points to the address of e. In (2), that value was changed to 5. However, when the values of *w and e were displayed, their values are different. But if you print value of w pointer and &e, they have the same value/address. How come e still contained 2, even if it was changed to 5? Were they stored in a separate location? Or a temporary? But how come the value pointed by w is still the address of e?

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  • sqrt(int_value + 0.0) -- Does it have a purpose?

    - by Earlz
    Hello, while doing some homework in my very strange C++ book, which I've been told before to throw away, had a very peculiar code segment. I know homework stuff always throws in extra "mystery" to try to confuse you like indenting 2 lines after a single-statement for-loop. But this one I'm confused on because it seems to serve some real-purpose. basically it is like this: int counter=10; ... if(pow(floor(sqrt(counter+0.0)),2) == counter) ... I'm interested in this part especially: sqrt(counter+0.0) Is there some purpose to the +0.0? Is this the poormans way of doing a static cast to a double? Does this avoid some compiler warning on some compiler I do not use? The entire program printed the exact same thing and compiled without warnings on g++ whenever I left out the +0.0 part. Maybe I'm not using a weird enough compiler? Edit: Also, does gcc just break standard and not make an error for Ambiguous reference since sqrt can take 3 different types of parameters? [earlz@EarlzBeta-~/projects/homework1] $ cat calc.cpp #include <cmath> int main(){ int counter=0; sqrt(counter); } [earlz@EarlzBeta-~/projects/homework1] $ g++ calc.cpp /usr/lib/libstdc++.so.47.0: warning: strcpy() is almost always misused, please use strlcpy() /usr/lib/libstdc++.so.47.0: warning: strcat() is almost always misused, please use strlcat() [earlz@EarlzBeta-~/projects/homework1] $

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  • Reference-type conversion operators: asking for trouble?

    - by Ben
    When I compile the following code using g++ class A {}; void foo(A&) {} int main() { foo(A()); return 0; } I get the following error messages: > g++ test.cpp -o test test.cpp: In function ‘int main()’: test.cpp:10: error: invalid initialization of non-const reference of type ‘A&’ from a temporary of type ‘A’ test.cpp:6: error: in passing argument 1 of ‘void foo(A&)’ After some reflection, these errors make plenty of sense to me. A() is just a temporary value, not an assignable location on the stack, so it wouldn't seem to have an address. If it doesn't have an address, then I can't hold a reference to it. Okay, fine. But wait! If I add the following conversion operator to the class A class A { public: operator A&() { return *this; } }; then all is well! My question is whether this even remotely safe. What exactly does this point to when A() is constructed as a temporary value? I am given some confidence by the fact that void foo(const A&) {} can accept temporary values according to g++ and all other compilers I've used. The const keyword can always be cast away, so it would surprise me if there were any actual semantic differences between a const A& parameter and an A& parameter. So I guess that's another way of asking my question: why is a const reference to a temporary value considered safe by the compiler whereas a non-const reference is not?

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  • How to use Common Table Expression and check no duplication in sqlserver

    - by vodkhang
    I have a table references to itself. User table: id, username, managerid and managerid links back to id Now, I want to get all the managers including direct manager, manager of direct manager, so on and so forth... The problem is that I do not want to have a unstop recursive sql. So, I want to check if an id alreay in a list, I will not include it anymore. Here is my sql for that: with --the relation for all the subparts of ozsolar including itself all_managers (id, username, managerid, idlist) as ( --seed that is the ozsola part select u1.id, u1.username, u1.managerid, ' ' from users u1, users u2 where u1.id = u2.managerid and u2.id = 6 UNION ALL select u.id, u.username, u.managerid, idlist + ' ' + u.id from all_managers a, users u where a.managerid = u.id and charindex(cast(u.id as nvarchar(5)), idlist) != 0 ) --select the total number of subparts and group by subpart select id, username from all_managers; The problem is that in this line: select u1.id, u1.username, u1.managerid, ' ' The sqlserver complains with me that I can not put ' ' as the initialized for idlist. nvarchar(40) does not work as well. I do not know how to declare it inside a common table expression like this one. Usually, in db2, I can just put varchar(40)

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  • How to access generic property without knowing the closed generic type

    - by Martin Booka Weser
    I have a generic Type as follows public class TestGeneric<T> { public T Data { get; set; } public TestGeneric(T data) { this.Data = data; } } If i have now an object (which is coming from some external source) from which i know that it's type is of some closed TestGeneric<, but i don't know the TypeParameter T. Now I need to access the Data of my object. Problem is that i can't cast the object, since i don't know exactly to which closed TestGeneric. I use // thx to http://stackoverflow.com/questions/457676/c-reflection-check-if-a-class-is-derived-from-a-generic-class private static bool IsSubclassOfRawGeneric(Type rawGeneric, Type subclass) { while (subclass != typeof(object)) { var cur = subclass.IsGenericType ? subclass.GetGenericTypeDefinition() : subclass; if (rawGeneric == cur) { return true; } subclass = subclass.BaseType; } return false; } to make sure, my object is of the generic type. The code in question is as follows: public static void Main() { object myObject = new TestGeneric<string>("test"); // or from another source if (IsSubclassOfRawGeneric(typeof(TestGeneric<>), myObject.GetType())) { // the following gives an InvalidCastException // var data = ((TestGeneric<object>)myObject).Data; // if i try to access the property with reflection // i get an InvalidOperationException var dataProperty = typeof(TestGeneric<>).GetProperty("Data"); object data = dataProperty.GetValue(myObject, new object[] { }); } } I need the Data regardless of its type (well, if i could ask for its type using GetType() would be fine, but not necessary) since i just want to dump it in xml using ToString(). Any suggestions? Thanx.

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  • Can't get SFTP to work in PHP

    - by Chris Kloberdanz
    I am writing a simple SFTP client in PHP because we have the need to programatically retrieve files via n remote servers. I am using the PECL SSH2 extension. I have run up against a road block, though. The documentation on php.net suggests that you can do this: $stream = fopen("ssh2.sftp://$sftp/path/to/file", 'r'); However, I have an ls method that attempts to something similar public function ls($dir) { $rd = "ssh2.sftp://{$this->sftp}/$dir"; $handle = opendir($rd); if (!is_resource($handle)) { throw new SFTPException("Could not open directory."); } while (false !== ($file = readdir($handle))) { if (substr($file, 0, 1) != '.'){ print $file . "\n"; } } closedir($handle); } I get the following error: PHP Warning: opendir(): Unable to open ssh2.sftp://Resource id #5/outgoing on remote host This makes perfect sense because that's what happens when you cast a resource to string. Is the documentation wrong? I tried replacing the resource with host, username, and host and that didn't work either. I know the path is correct because I can run SFTP from the command line and it works fine. Has anyone else tried to use the SSH2 extenstion with SFTP? Am I missing something obvious here? UPDATE: I setup sftp on another machine in-house and it works just fine. So, there must be something about the server I am trying to connect to that isn't working.

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  • How can I read a DBF file with incorrectly defined column data types using ADO.NET?

    - by Jason
    I have a several DBF files generated by a third party that I need to be able to query. I am having trouble because all of the column types have been defined as characters, but the data within some of these fields actually contain binary data. If I try to read these fields using an OleDbDataReader as anything other than a string or character array, I get an InvalidCastException thrown, but I need to be able to read them as a binary value or at least cast/convert them after they are read. The columns that actually DO contain text are being returned as expected. For example, the very first column is defined as a character field with a length of 2 bytes, but the field contains a 16-bit integer. I have written the following test code to read the first column and convert it to the appropriate data type, but the value is not coming out right. The first row of the database has a value of 17365 (0x43D5) in the first column. Running the following code, what I end up getting is 17215 (0x433F). I'm pretty sure it has to do with using the ASCII encoding to get the bytes from the string returned by the data reader, but I'm not sure of another way to get the value into the format that I need, other that to write my own DBF reader and bypass ADO.NET altogether which I don't want to do unless I absolutely have to. Any help would be greatly appreciated. byte[] c0; int i0; string con = @"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\ASTM;Extended Properties=dBASE III;User ID=Admin;Password=;"; using (OleDbConnection c = new OleDbConnection(con)) { c.Open(); OleDbCommand cmd = c.CreateCommand(); cmd.CommandText = "SELECT * FROM astm2007"; OleDbDataReader dr = cmd.ExecuteReader(); while (dr.Read()) { c0 = Encoding.ASCII.GetBytes(dr.GetValue(0).ToString()); i0 = BitConverter.ToInt16(c0, 0); } dr.Dispose(); }

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  • Why ClassCastException on JMS ConnectionFactory lookup in JNDI?

    - by Derek Mahar
    What might be the cause of the following ClassCastException in a standalone JMS client application when it attempts to retrieve a connection factory from the JNDI provider? Exception in thread "main" java.lang.ClassCastException: javax.naming.Reference cannot be cast to javax.jms.ConnectionFactory Here is an abbreviated version of the JMS client that includes only its start() and stop() methods. The exception occurs on the first line in method start() which attempts to retrieve the connection factory from the JNDI provider, a remote LDAP server. The JMS connection factory and destination objects are on a remote JMS server. class JmsClient { private ConnectionFactory connectionFactory; private Connection connection; private Session session; private MessageConsumer consumer; private Topic topic; public void stop() throws JMSException { consumer.close(); session.close(); connection.close(); } public void start(Context context, String connectionFactoryName, String topicName) throws NamingException, JMSException { // ClassCastException occurs when retrieving connection factory. connectionFactory = (ConnectionFactory) context.lookup(connectionFactoryName); connection = connectionFactory.createConnection("username","password"); session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE); topic = (Topic) context.lookup(topicName); consumer = session.createConsumer(topic); connection.start(); } private static Context getInitialContext() throws NamingException, IOException { String filename = "context.properties"; Properties props = new Properties(); props.load(new FileInputStream(filename)); return new InitialContext(props); } }

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  • How to call a .NET COM method with an array from delphi using PSafeArray?

    - by Sebastian Godelet
    Hello. I have an .NET (4.0) interface which is implemented with a ServicedComponent COM+ class: interface DotNetIface { void MethodRef(var System.Guid guid); void MethodArray(System.Guid[] guids, params object[] parameters); void MethodCStyle([MarshalAs(UnmanagedType.LPArray, ArraySubType=UnmanagedType.Struct, SizeConst=5)]System.Guid[] guids); } Now I used the Delphi 2007 import wizard to import the type library, and as expected I get the following signatures: procedure MethodRef(var guid : TGuid); procedure MethodArray(guids : PSafeArray); procedure MethodCStyle(var guids : ClrGuid /* from mscorlib_TLB */); If i now call the "ref" method like this it works fine: procedure CallByRef(guid : TGuid); var test : TGuid; begin test := ... comRef.MethodRef(guid); end; Now I also need the array method procedure CallArray(); var localGuid : TGuid; arrayVariant : OleVariant; begin arrayVariant := VarArrayCreate([0,4], varVariant /* dont know here */); arrayVariant[0] := localGuid; /* compile error, cannot cast implicitly */ comRef.MethodArray(PSafeArray(TVarData(arrayVariant.VArray)), /* here this object... PSafeArray works actually*/); end; Now lastly i tried with a c array procedure CallCStyle(); var localGuid : TGuid; arrayOfGuid : array [0..4] of ClrGuid; begin arrayOfGuid[0] := ClrGuid(localGuid); comRef.MethodCStyle(PSafeArray(/* now i dont know put it*/, /* here this object... PSafeArray works actually*/); end; I seriously dont know how to make this work. I hope someone has more experience with COM marshalling thx Side node: I found VT_CLSID which i think can be passed for SafeArrayCreate, but I am not sure how to sue that

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  • SQL Server: Is it possible to prevent SQL Agent from failing a step on error?

    - by Kenneth
    I have a stored procedure that runs custom backups for around 60 SQL servers (mixes 2000 through 2008R2). Occasionally, due to issues outside of my control (backup device inaccessible, network error, etc.) an individual backup on one or two databases will fail. This causes this entire step to fail, which means any subsequent backup commands are not executed and half of the databases on a given server may not be backed up. On the 2005+ boxes I am using TRY/CATCH blocks to manage these problems and continue backing up the remaining databases. On a 2000 server however, for example, I have no way to prevent this error from failing the entire step: Msg 3201, Level 16, State 1, Line 1 Cannot open backup device 'db-diff(\PATH\DB-DIFF-03-16-2010.DIF)'. Operating system error 5(Access is denied.). Msg 3013, Level 16, State 1, Line 1 BACKUP DATABASE is terminating abnormally. I am simply asking if anything like TRY/CATCH is possible in SQL 2000? I realize there are no built in methods for this, so I guess I am looking for some creativity. Even when wrapping each backup (or any failing statement) via sp_executesql the job fails instantly. Example: DECLARE @x INT, @iReturn INT PRINT 'Executing statement that will fail with 208.' EXEC @iReturn = Sp_executesql N'SELECT * from TABLETHATDOESNTEXIST;' PRINT Cast(@iReturn AS NVARCHAR) --In SSMS this return code prints. Executed as a job it fails and aborts before this statement.

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  • Calling MethodBase's Invoke on a constructor (reflection)

    - by Alix
    Hi everyone. First of all, sorry if this has been asked before. I've done a pretty comprehensive search and found nothing quite like it, but I may have missed something. And now to the question: I'm trying to invoke a constructor through reflection, with no luck. Basically, I have an object that I want to clone, so I look up the copy constructor for its type and then want to invoke it. Here's what I have: public Object clone(Object toClone) { MethodBase copyConstructor = type.GetConstructor( new Type[] { toClone.GetType() }); return method.Invoke(toClone, new object[] { toClone }); //<-- doesn't work } I call the above method like so: List list = new List(new int[] { 0, 1, 2 }); List clone = (List) clone(list); Now, notice the invoke method I'm using is MethodBase's invoke. ConstructorInfo provides an invoke method that does work if invoked like this: return ((ConstructorInfo) method).Invoke(new object[] { toClone }); However, I want to use MethodBase's method, because in reality instead of looking up the copy constructor every time I will store it in a dictionary, and the dictionary contains both methods and constructors, so it's a Dictionary<MethodBase>, not Dictionary<ConstructorInfo>. I could of course cast to ConstructorInfo as I do above, but I'd rather avoid the casting and use the MethodBase method directly. I just can't figure out the right parameters. Any help? Thanks so much.

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  • Lazy non-modifiable list in Google Collections

    - by mindas
    I was looking for a decent implementation of a generic lazy non-modifiable list implementation to wrap my search result entries. The unmodifiable part of the task is easy as it can be achieved by Collections.unmodifiableList() so I only need to sort out the the lazy part. Surprisingly, google-collections doesn't have anything to offer; while LazyList from Apache Commons Collections does not support generics. I have found an attempt to build something on top of google-collections but it seems to be incomplete (e.g. does not support size()), outdated (does not compile with 1.0 final) and requiring some external classes, but could be used as a good starting point to build my own class. Is anybody aware of any good implementation of a LazyList? If not, which option do you think is better: write my own implementation, based on google-collections ForwardingList, similar to what Peter Maas did; write my own wrapper around Commons Collections LazyList (the wrapper would only add generics so I don't have to cast everywhere but only in the wrapper itself); just write something on top of java.util.AbstractList; Any other suggestions are welcome.

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  • Design considerations for temporarily transforming a player into an animal in a role playing game

    - by mikedev
    I am working on a role playing game for fun and to practice design patterns. I would like players to be able to transform themselves into different animals. For example, a Druid might be able to shape shift into a cheetah. Right now I'm planning on using the decorator pattern to do this but my question is - how do I make it so that when a druid is in the cheetah form, they can only access skills for the cheetah? In other words, they should not be able to access their normal Druid skills. Using the decorator pattern it appears that even in the cheetah form my druid will be able to access their normal druid skills. class Druid : Character { // many cool druid skills and spells void LightHeal(Character target) { } } abstract class CharacterDecorator : Character { Character DecoratedCharacter; } class CheetahForm : CharacterDecorator { Character DecoratedCharacter; public CheetahForm(Character decoratedCharacter) { DecoratedCharacter= decoratedCharacter; } // many cool cheetah related skills void CheetahRun() { // let player move very fast } } now using the classes Druid myDruid = new Druid(); myDruid.LightHeal(myDruid); // casting light heal here is fine myDruid = new CheetahForm(myDruid); myDruid.LightHeal(myDruid); // casting here should not be allowed Hmmmm...now that I think about it, will myDruid be unable to us the Druid class spells/skills unless the class is down-casted? But even if that's the case, is there a better way to ensure that myDruid at this point is locked out from all Druid related spells/skills until it is cast back to a Druid (since currently it's in CheetahForm)

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  • Using MinHash to find similiarities between 2 images

    - by Sung Meister
    I am using MinHash algorithm to find similar images between images. I have run across this post, How can I recognize slightly modified images? which pointed me to MinHash algorithm. Being a bit mathematically challenged, I was using a C# implementation from this blog post, Set Similarity and Min Hash. But while trying to use the implementation, I have run into 2 problems. What value should I set universe value to? When passing image byte array to HashSet, it only contains distinct byte values; thus comparing values from 1 ~ 256. What is this universe in MinHash? And what can I do to improve the C# MinHash implementation? Since HashSet<byte> contains values upto 256, similarity value always come out to 1. Here is the source that uses the C# MinHash implementation from Set Similarity and Min Hash: class Program { static void Main(string[] args) { var imageSet1 = GetImageByte(@".\Images\01.JPG"); var imageSet2 = GetImageByte(@".\Images\02.TIF"); //var app = new MinHash(256); var app = new MinHash(Math.Min(imageSet1.Count, imageSet2.Count)); double imageSimilarity = app.Similarity(imageSet1, imageSet2); Console.WriteLine("similarity = {0}", imageSimilarity); } private static HashSet<byte> GetImageByte(string imagePath) { using (var fs = new FileStream(imagePath, FileMode.Open, FileAccess.Read)) using (var br = new BinaryReader(fs)) { //List<int> bytes = br.ReadBytes((int)fs.Length).Cast<int>().ToList(); var bytes = new List<byte>(br.ReadBytes((int) fs.Length).ToArray()); return new HashSet<byte>(bytes); } } }

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  • How to get rid of void-pointers.

    - by Patrick
    I inherited a big application that was originally written in C (but in the mean time a lot of C++ was also added to it). Because of historical reasons, the application contains a lot of void-pointers. Before you start to choke, let me explain why this was done. The application contains many different data structures, but they are stored in 'generic' containers. Nowadays I would use templated STL containers for it, or I would give all data structures a common base class, so that the container can store pointers to the base class, but in the [good?] old C days, the only solution was to cast the struct-pointer to a void-pointer. Additionally, there is a lot of code that works on these void-pointers, and uses very strange C constructions to emulate polymorphism in C. I am now reworking the application, and trying to get rid of the void-pointers. Adding a common base-class to all the data structures isn't that hard (few days of work), but the problem is that the code is full of constructions like shown below. This is an example of how data is stored: void storeData (int datatype, void *data); // function prototype ... Customer *myCustomer = ...; storeData (TYPE_CUSTOMER, myCustomer); This is an example of how data is fetched again: Customer *myCustomer = (Customer *) fetchData (int datatype, char *key); I actually want to replace all the void-pointers with some smart-pointer (reference-counted), but I can't find a trick to automate (or at least) help me to get rid of all the casts to and from void-pointers. Any tips on how to find, replace, or interact in any possible way with these conversions?

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  • Converting an integer to a boxed enum type only known at runtime

    - by Marc Gravell
    Imagine we have an enum: enum Foo { A=1,B=2,C=3 } If the type is known at compile-time, a direct cast can be used to change between the enum-type and the underlying type (usually int): static int GetValue() { return 2; } ... Foo foo = (Foo)GetValue(); // becomes Foo.B And boxing this gives a box of type Foo: object o1 = foo; Console.WriteLine(o1.GetType().Name); // writes Foo (and indeed, you can box as Foo and unbox as int, or box as int and unbox as Foo quite happily) However (the problem); if the enum type is only known at runtime things are... trickier. It is obviously trivial to box it as an int - but can I box it as Foo? (Ideally without using generics and MakeGenericMethod, which would be ugly). Convert.ChangeType throws an exception. ToString and Enum.Parse works, but is horribly inefficient. I could look at the defined values (Enum.GetValues or Type.GetFields), but that is very hard for [Flags], and even without would require getting back to the underlying-type first (which isn't as hard, thankfully). But; is there a more direct to get from a value of the correct underlying-type to a box of the enum-type, where the type is only known at runtime?

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  • Mapping self-table one-to-many using non-PK clolumns

    - by Harel Moshe
    Hey, i have a legacy DB to which a Person object is mapped, having a collection of family-members, like this: class Person { ... string Id; /* 9-digits string */ IList<Person> Family; ... } The PERSON table seems like: Id: CHAR(9), PK FamilyId: INT, NOT NULL and several other non-relevant columns. I'm trying to map the Family collection to the PERSON table using the FamilyId column, which is not the PK as mentioned above. So, i actually have a one-to-many which is self-table-referential. I'm getting an error saying 'Cast is not valid' when my mapping looks like this: ... <set name="Family" table="Person" lazy="false"> <key column="FamilyId" /> <one-to-many class="Person" /> </set> ... because obviously, the join NHibernate is trying to make is between the PK column, Id, and the 'secondary' column, FamilyId, instead of joining the FamilyId column to itself. Any ideas please?

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  • How to put foreign key constraints on a computed fields in sql server?

    - by Asaf R
    Table A has a computed field called Computed1. It's persisted and not null. Also, it always computes to an expression which is char(50). It's also unique and has a unique key constraint on it. Table B has a field RefersToComputed1, which should refer to a valid Computed1 value. Trying to create a foreign key constraint on B's RefersToComputed1 that references A' Computed1 leads to the following error: Error SQL01268: .Net SqlClient Data Provider: Msg 1753, Level 16, State 0, Line 1 Column 'B.RefersToComputed1' is not the same length or scale as referencing column 'A.Computed1' in foreign key 'FK_B_A'. Columns participating in a foreign key relationship must be defined with the same length and scale. Q: Why is this error created? Are there special measures needed for foreign keys for computed columns, and if so what are they? Summary: The specific problem rises from computed, char based, fields being varchar. Hence, Computed1 is varchar(50) and not char(50). It's best to have a cast surrounding a computed field's expression to force it to a specific type. Credit goes to Cade Roux for this tip.

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  • handling DATETIME values 0000-00-00 00:00:00 in JDBC

    - by Jason S
    I get an exception (see below) if I try to do resultset.getString("add_date"); for a JDBC connection to a MySQL database containing a DATETIME value of 0000-00-00 00:00:00 (the quasi-null value for DATETIME), even though I'm just trying to get the value as string, not as an object. I got around this by doing SELECT CAST(add_date AS CHAR) as add_date which works, but seems silly... is there a better way to do this? My point is that I just want the raw DATETIME string, so I can parse it myself as is. note: here's where the 0000 comes in: (from http://dev.mysql.com/doc/refman/5.0/en/datetime.html) Illegal DATETIME, DATE, or TIMESTAMP values are converted to the “zero” value of the appropriate type ('0000-00-00 00:00:00' or '0000-00-00'). The specific exception is this one: SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. SQLState: S1009 VendorError: 0 java.sql.SQLException: Cannot convert value '0000-00-00 00:00:00' from column 5 to TIMESTAMP. at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1055) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:956) at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:926) at com.mysql.jdbc.ResultSetImpl.getTimestampFromString(ResultSetImpl.java:6343) at com.mysql.jdbc.ResultSetImpl.getStringInternal(ResultSetImpl.java:5670) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5491) at com.mysql.jdbc.ResultSetImpl.getString(ResultSetImpl.java:5531)

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