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  • Why does autoboxing in Java allow me to have 3 possible values for a boolean?

    - by John
    Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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  • OneToOne JPA / Hibernate eager loading cause N+1 select

    - by Alexandre Lavoie
    I created a method to have multilingual text on different objects without creating field for each languages or tables for each objects types. Now the only problem I've got is N+1 select queries when doing a simple loading. Tables schema : CREATE TABLE `testentities` ( `keyTestEntity` int(11) NOT NULL, `keyMultilingualText` int(11) NOT NULL, PRIMARY KEY (`keyTestEntity`) ) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8; CREATE TABLE `common_multilingualtexts` ( `keyMultilingualText` int(11) NOT NULL auto_increment, PRIMARY KEY (`keyMultilingualText`) ) ENGINE=MyISAM AUTO_INCREMENT=0 DEFAULT CHARSET=utf8; CREATE TABLE `common_multilingualtexts_values` ( `languageCode` varchar(5) NOT NULL, `keyMultilingualText` int(11) NOT NULL, `value` text, PRIMARY KEY (`languageCode`,`keyMultilingualText`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; MultilingualText.java @Entity @Table(name = "common_multilingualtexts") public class MultilingualText implements Serializable { private Integer m_iKeyMultilingualText; private Map<String, String> m_lValues = new HashMap<String, String>(); public void setKeyMultilingualText(Integer p_iKeyMultilingualText) { m_iKeyMultilingualText = p_iKeyMultilingualText; } @Id @GeneratedValue @Column(name = "keyMultilingualText") public Integer getKeyMultilingualText() { return m_iKeyMultilingualText; } public void setValues(Map<String, String> p_lValues) { m_lValues = p_lValues; } @ElementCollection(fetch = FetchType.EAGER) @CollectionTable(name = "common_multilingualtexts_values", joinColumns = @JoinColumn(name = "keyMultilingualText")) @MapKeyColumn(name = "languageCode") @Column(name = "value") public Map<String, String> getValues() { return m_lValues; } public void put(String p_sLanguageCode, String p_sValue) { m_lValues.put(p_sLanguageCode,p_sValue); } public String get(String p_sLanguageCode) { if(m_lValues.containsKey(p_sLanguageCode)) { return m_lValues.get(p_sLanguageCode); } return null; } } And it is used like this on a object (having a foreign key to the multilingual text) : @Entity @Table(name = "testentities") public class TestEntity implements Serializable { private Integer m_iKeyEntity; private MultilingualText m_oText; public void setKeyEntity(Integer p_iKeyEntity) { m_iKeyEntity = p_iKeyEntity; } @Id @GeneratedValue @Column(name = "keyEntity") public Integer getKeyEntity() { return m_iKeyEntity; } public void setText(MultilingualText p_oText) { m_oText = p_oText; } @OneToOne(cascade = CascadeType.ALL) @JoinColumn(name = "keyText") public MultilingualText getText() { return m_oText; } } Now, when doing a simple HQL query : from TestEntity, I get a query selecting TestEntity's and one query for each MultilingualText that need to be loaded on each TestEntity. I've searched a lot and found absolutely no solutions. I have tested : @Fetch(FetchType.JOIN) optional = false @ManyToOne instead of @OneToOne Now I am out of idea!

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  • GetOleDbSchemaTable Foreign Keys on Sql Server 2005

    - by haxelit
    I'm trying to get the Foreign Keys for a table in my SQL Server 2005 database. I'm using the GetOleDbSchemaTable function right now: DataTable schemaTable = connection.GetOleDbSchemaTable( OleDbSchemaGuid.Foreign_Keys, new object[] { null, null, null, "TABLE" }); This pulls back the right foreign keys, the only problem is that the UpdateRule and DeleteRule are set to "No Action". If I browse to the same table in SSMS I can see that my DeleteRule is "Set NULL". Does the GetOleDbSchemaTable function not return the proper foreign key rules ? Has any one else ran into this problem ?

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  • Invalid argument when calling linux splice()

    - by benny wallace
    Hi I wanted to try out the splice syscall. I have this function - it should copy content of one file to another: static void test_splice( int in, int out ) { int i = 0, rcvd = 0; int filedes[2]; off_t off = 0; if ( pipe( filedes ) < 0 ) { perror( "Kicha pipe" ); exit( EXIT_FAILURE ); } for ( i = 0; i < NUMLOOPS; ++i ) { if ( ( rcvd = splice( in, NULL, filedes[1], NULL, BUFSIZE, SPLICE_F_MORE | SPLICE_F_MOVE ) ) < 0 ) { perror( "splice" ); exit( EXIT_FAILURE ); } if ( splice( filedes[0], NULL, out, NULL, rcvd, SPLICE_F_MORE | SPLICE_F_MOVE ) < 0 ) { perror( "splice" ); exit( EXIT_FAILURE ); } } } The second call to splice in first iteration returns EINVAL ( invalid argument from perror ) everytime - what could be the reason?

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  • T-SQL - Left Outer Joins - Fileters in the where clause versus the on clause.

    - by Greg Potter
    I am trying to compare two tables to find rows in each table that is not in the other. Table 1 has a groupby column to create 2 sets of data within table one. groupby number ----------- ----------- 1 1 1 2 2 1 2 2 2 4 Table 2 has only one column. number ----------- 1 3 4 So Table 1 has the values 1,2,4 in group 2 and Table 2 has the values 1,3,4. I expect the following result when joining for Group 2: `Table 1 LEFT OUTER Join Table 2` T1_Groupby T1_Number T2_Number ----------- ----------- ----------- 2 2 NULL `Table 2 LEFT OUTER Join Table 1` T1_Groupby T1_Number T2_Number ----------- ----------- ----------- NULL NULL 3 The only way I can get this to work is if I put a where clause for the first join: PRINT 'Table 1 LEFT OUTER Join Table 2, with WHERE clause' select table1.groupby as [T1_Groupby], table1.number as [T1_Number], table2.number as [T2_Number] from table1 LEFT OUTER join table2 --****************************** on table1.number = table2.number --****************************** WHERE table1.groupby = 2 AND table2.number IS NULL and a filter in the ON for the second: PRINT 'Table 2 LEFT OUTER Join Table 1, with ON clause' select table1.groupby as [T1_Groupby], table1.number as [T1_Number], table2.number as [T2_Number] from table2 LEFT OUTER join table1 --****************************** on table2.number = table1.number AND table1.groupby = 2 --****************************** WHERE table1.number IS NULL Can anyone come up with a way of not using the filter in the on clause but in the where clause? The context of this is I have a staging area in a database and I want to identify new records and records that have been deleted. The groupby field is the equivalent of a batchid for an extract and I am comparing the latest extract in a temp table to a the batch from yesterday stored in a partioneds table, which also has all the previously extracted batches as well. Code to create table 1 and 2: create table table1 (number int, groupby int) create table table2 (number int) insert into table1 (number, groupby) values (1, 1) insert into table1 (number, groupby) values (2, 1) insert into table1 (number, groupby) values (1, 2) insert into table2 (number) values (1) insert into table1 (number, groupby) values (2, 2) insert into table2 (number) values (3) insert into table1 (number, groupby) values (4, 2) insert into table2 (number) values (4)

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  • AutoIncrement in SQLite with Subsonic 3

    - by Cooter
    This is probably a simple matter, but when I create a new object, the ID property starts off as 0 rather than null. As I understand it, SQLite takes/needs a value of null for the PK column to do the AutoIncrement. So the short question is how to get the ID in the object to start life as null? Thanks cooter

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  • NHibernate Oracle stored procedure problem

    - by Mr. Flint
    ------Using VS2008, ASP.Net with C#, Oracle, NHibernate---- I have tested my stored procedure. It's working but not with NHibernate. Here are the codes: Procedure : create or replace procedure ThanaDelete (id number) as begin delete from thana_tbl where thana_code = id; end Mapping File: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="DataTransfer" namespace="DataTransfer"> <class name="DataTransfer.Models.Thana, DataTransfer" table="THANA_TBL"> <id name="THANA_CODE" column="THANA_CODE" type="Int32" unsaved-value="0"> <generator class="native"> <param name="sequence"> SEQ_TEST </param> </generator> </id> <property name="THANA_NAME" column="THANA_NAME" type="string" not-null="false"/> <property name="DISTRICT_CODE" column="DISTRICT_CODE" type="Int32" not-null="false"/> <property name="USER_ID" column="USER_ID" type="string" not-null="false"/> <property name="TRANSACTION_DATE" column="TRANSACTION_DATE" type="Date" not-null="false"/> <property name="TRANSACTION_TIME" column="TRANSACTION_TIME" type="string" not-null="false"/> <sql-delete>exec THANADELETE ? </sql-delete> </class> </hibernate-mapping> error: Message: could not delete: [DataTransfer.Models.Thana#10][SQL: exec THANADELETE ?] Source: NHibernate Inner Exception System.Data.OracleClient.OracleException Message: ORA-00900: invalid SQL statement

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  • ASP.Net HttpModule List<> content

    - by test
    We have created an http module that loads data on initialize into a list, and uses that list on every endrequest event of application. However we got a null reference exception on the module at endRequest event complaining that the content is null. Yet we are sure that at module initialization we have put non-null objects correctly. How is this possible? Any ideas? Thanks in advance. The place where i fill the data into the list what named as "Pages" : using (SqlDataReader reader = cmd.ExecuteReader()) { while (reader.Read()) { LandingPageDetails details = new LandingPageDetails(); details.DomainId = Convert.ToInt32(reader["DomainId"]); details.PageId = Convert.ToInt32(reader["TrackingPageId"]); details.PageAddress = Convert.ToString(reader["PageAddress"]); if (!string.IsNullOrEmpty(details.PageAddress)) { Pages.Add(details); } } } // Find the related record on EndRequesst event LandingPageDetails result = Pages.Find ( delegate(LandingPageDetails current) { return current.PageAddress.Equals(url, StringComparison.InvariantCultureIgnoreCase); } ); The line what we get the error return current.PageAddress.Equals(url, StringComparison.InvariantCultureIgnoreCase); "current" is the null object P.S : It works properly, but one day later contents become null. Possibly, there is something wrong on IIS. Our server is Windows 2003, IIS 6.0

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  • BST insert operation. don't insert a node if a duplicate exists already

    - by jeev
    the following code reads an input array, and constructs a BST from it. if the current arr[i] is a duplicate, of a node in the tree, then arr[i] is discarded. count in the struct node refers to the number of times a number appears in the array. fi refers to the first index of the element found in the array. after the insertion, i am doing a post-order traversal of the tree and printing the data, count and index (in this order). the output i am getting when i run this code is: 0 0 7 0 0 6 thank you for your help. Jeev struct node{ int data; struct node *left; struct node *right; int fi; int count; }; struct node* binSearchTree(int arr[], int size); int setdata(struct node**node, int data, int index); void insert(int data, struct node **root, int index); void sortOnCount(struct node* root); void main(){ int arr[] = {2,5,2,8,5,6,8,8}; int size = sizeof(arr)/sizeof(arr[0]); struct node* temp = binSearchTree(arr, size); sortOnCount(temp); } struct node* binSearchTree(int arr[], int size){ struct node* root = (struct node*)malloc(sizeof(struct node)); if(!setdata(&root, arr[0], 0)) fprintf(stderr, "root couldn't be initialized"); int i = 1; for(;i<size;i++){ insert(arr[i], &root, i); } return root; } int setdata(struct node** nod, int data, int index){ if(*nod!=NULL){ (*nod)->fi = index; (*nod)->left = NULL; (*nod)->right = NULL; return 1; } return 0; } void insert(int data, struct node **root, int index){ struct node* new = (struct node*)malloc(sizeof(struct node)); setdata(&new, data, index); struct node** temp = root; while(1){ if(data<=(*temp)->data){ if((*temp)->left!=NULL) *temp=(*temp)->left; else{ (*temp)->left = new; break; } } else if(data>(*temp)->data){ if((*temp)->right!=NULL) *temp=(*temp)->right; else{ (*temp)->right = new; break; } } else{ (*temp)->count++; free(new); break; } } } void sortOnCount(struct node* root){ if(root!=NULL){ sortOnCount(root->left); sortOnCount(root->right); printf("%d %d %d\n", (root)->data, (root)->count, (root)->fi); } }

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  • How the JOptionPane works

    - by DevAno1
    How can I control what happens with window after clicking JOPtionPane buttons ? I'm trying to implement simple file chooser. In my frame I have 3 buttons (OK, Cancel, Browse). Browse button opens file search window, and after picking files should return to main frame. Clicking OK will open a frame with the content of the file. Now porblem looks this way. With the code below, I can choose file but directly after that a new frame is created, and my frame with buttons dissapears : import java.io.File; import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.awt.*; import javax.swing.*; import java.io.*; public class Main { public static void main(String args[]) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { show("Window"); } }); } public static void show(String frame_name){ JFrame frame = new JFrame(frame_name); frame.setPreferredSize(new Dimension(450, 300)); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel top = new JPanel(); top.setLayout(new BoxLayout(top, BoxLayout.Y_AXIS)); JFileChooser fc = new JFileChooser(new File(".")); JPanel creator = new JPanel(); creator.setLayout(new BoxLayout(creator, BoxLayout.Y_AXIS)); creator.add(top); String[] buttons = {"OK", "Cancel", "Browse"}; int rc = JOptionPane.showOptionDialog( null, creator, frame_name, JOptionPane.DEFAULT_OPTION, JOptionPane.PLAIN_MESSAGE, null, buttons, buttons[0] ); String approveButt = ""; switch(rc){ case 0: break; case 1: break; case 2: approveButt = buttons[rc]; int retVal = fc.showDialog(null, approveButt); if (retVal == JFileChooser.APPROVE_OPTION) System.out.println(approveButt + " " + fc.getSelectedFile()); break; } frame.pack(); frame.setVisible(true); } } With the second code I can return to my menu, but in no way I am able to pop this new frame, which appeared with first code. How to control this ? What am I missing ? public class Main { public static void main(String args[]) { javax.swing.SwingUtilities.invokeLater(new Runnable() { public void run() { show("Window"); } }); } public static void show(String frame_name){ JFrame frame = new JFrame(frame_name); frame.setPreferredSize(new Dimension(450, 300)); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); JPanel top = new JPanel(); top.setLayout(new BoxLayout(top, BoxLayout.Y_AXIS)); JFileChooser fc = new JFileChooser(new File(".")); JPanel creator = new JPanel(); creator.setLayout(new BoxLayout(creator, BoxLayout.Y_AXIS)); creator.add(top); String[] buttons = {"OK", "Cancel", "Browse"}; String approveButt = ""; Plane m = null; int rc = -1; while (rc != 0) { rc = JOptionPane.showOptionDialog( null, creator, frame_name, JOptionPane.DEFAULT_OPTION, JOptionPane.PLAIN_MESSAGE, null, buttons, buttons[0] ); switch (rc) { case 0: m = new Plane(); case 1: System.exit(0); case 2: approveButt = buttons[rc]; int retVal = fc.showDialog(null, approveButt); if (retVal == JFileChooser.APPROVE_OPTION) System.out.println(approveButt + " " + fc.getSelectedFile()); break; default: break; } } addComponents(frame.getContentPane(), m); frame.pack(); frame.setVisible(true); } private static void addComponents(Container c, Plane e) { c.setLayout(new BoxLayout(c, BoxLayout.Y_AXIS)); c.add(e); } } class Plane extends JPanel { public Plane(){ } @Override public void paint(Graphics g){ g.setColor(Color.BLUE); g.fillRect(0, 0, 400, 250); } }

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  • C# Reflection - Casting private Object field

    - by alhazen
    I have the following classes: public class MyEventArgs : EventArgs { public object State; public MyEventArgs (object state) { this.State = state; } } public class MyClass { // ... public List<string> ErrorMessages { get { return errorMessages; } } } When I raise my event, I set 'State' of the MyEventArgs object to an object of type MyClass. I'm trying to retrieve ErrorMessages by reflection in my event handler: public static void OnEventEnded(object sender, EventArgs args) { Type type = args.GetType(); FieldInfo stateInfo = type.GetField("State"); PropertyInfo errorMessagesInfo = stateInfo.FieldType.GetProperty("ErrorMessages"); object errorMessages = errorMessagesInfo.GetValue(null, null); } But this returns errorMessagesInfo as null (even though stateInfo is not null). Is it possible to retrieve ErrorMessages ? Thank you

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  • Retrive treeview item

    - by Anu
    Hi, In y treeview i have text,after i seelcted that,i want to retrive that selected item as string and i need to pass this string to various fucntions. I dont know how to get the selected item.I coded like private void treeview1_SelectedItemChanged(object sender, RoutedPropertyChangedEventArgs<object> e) { TreeViewItem selectedTVI = null; if (treeview1.SelectedItem != null) { selectedTVI = treeview1.Tag as TreeViewItem; } } But selectedTVi shows NULL.What can i do?

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  • mysql: Average over multiple columns in one row, ignoring nulls

    - by Sai Emrys
    I have a large table (of sites) with several numeric columns - say a through f. (These are site rankings from different organizations, like alexa, google, quantcast, etc. Each has a different range and format; they're straight dumps from the outside DBs.) For many of the records, one or more of these columns is null, because the outside DB doesn't have data for it. They all cover different subsets of my DB. I want column t to be their weighted average (each of a..f have static weights which I assign), ignoring null values (which can occur in any of them), except being null if they're all null. I would prefer to do this with a simple SQL calculation, rather than doing it in app code or using some huge ugly nested if block to handle every permutation of nulls. (Given that I have an increasing number of columns to average over as I add in more outside DB sources, this would be exponentially more ugly and bug-prone.) I'd use AVG but that's only for group by, and this is w/in one record. The data is semantically nullable, and I don't want to average in some "average" value in place of the nulls; I want to only be counting the columns for which data is there. Is there a good way to do this? Ideally, what I want is something like UPDATE sites SET t = AVG(a*a_weight,b*b_weight,...) where any null values are just ignored and no grouping is happening.

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  • Data tweaking code runs fine when executed directly - but never stops when used in trigger

    - by MBaas
    I have written some code to ensure that items on an order are all numbered (the "position number" or "item number" has been introduced only recently and we did not want to go and change all related code - as it is "asthetics only" and has no functional impact.) So, the idea is to go and check for an records that jave an itemno of NULL or 0 - and then compute one and assign it. When executing this code in a query window, it works fine. When putting it into an AFTER INSERT-trigger, it loops forever. So what is wrong here? /****** Objekt: Trigger [SetzePosNr] Skriptdatum: 02/28/2010 20:06:29 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TRIGGER [SetzePosNr] ON [dbo].[bestellpos] AFTER INSERT AS BEGIN DECLARE @idb int DECLARE @idp int DECLARE @pnr int SELECT @idp=id,@idb=id_bestellungen FROM bestellpos WHERE posnr IS NULL OR posnr=0 WHILE @idp IS NOT NULL BEGIN SELECT @pnr = 1+max(posnr) FROM bestellpos WHERE id_bestellungen = @idb print( 'idp=' + str(@idp) + ', idb=' + str(@idb) + ', posnr=' + str(@pnr)) UPDATE bestellpos SET posnr=@pnr WHERE id=@idp SELECT @idp=id,@idb=id_bestellungen FROM bestellpos WHERE posnr IS NULL OR posnr=0 END END

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  • Restoring multiple database backups in a transaction

    - by Raghu Dodda
    I wrote a stored procedure that restores as set of the database backups. It takes two parameters - a source directory and a restore directory. The procedure looks for all .bak files in the source directory (recursively) and restores all the databases. The stored procedure works as expected, but it has one issue - if I uncomment the try-catch statements, the procedure terminates with the following error: error_number = 3013 error_severity = 16 error_state = 1 error_message = DATABASE is terminating abnormally. The weird part is sometimes (it is not consistent) the restore is done even if the error occurs. The procedure: create proc usp_restore_databases ( @source_directory varchar(1000), @restore_directory varchar(1000) ) as begin declare @number_of_backup_files int -- begin transaction -- begin try -- step 0: Initial validation if(right(@source_directory, 1) <> '\') set @source_directory = @source_directory + '\' if(right(@restore_directory, 1) <> '\') set @restore_directory = @restore_directory + '\' -- step 1: Put all the backup files in the specified directory in a table -- declare @backup_files table ( file_path varchar(1000)) declare @dos_command varchar(1000) set @dos_command = 'dir ' + '"' + @source_directory + '*.bak" /s/b' /* DEBUG */ print @dos_command insert into @backup_files(file_path) exec xp_cmdshell @dos_command delete from @backup_files where file_path IS NULL select @number_of_backup_files = count(1) from @backup_files /* DEBUG */ select * from @backup_files /* DEBUG */ print @number_of_backup_files -- step 2: restore each backup file -- declare backup_file_cursor cursor for select file_path from @backup_files open backup_file_cursor declare @index int; set @index = 0 while(@index < @number_of_backup_files) begin declare @backup_file_path varchar(1000) fetch next from backup_file_cursor into @backup_file_path /* DEBUG */ print @backup_file_path -- step 2a: parse the full backup file name to get the DB file name. declare @db_name varchar(100) set @db_name = right(@backup_file_path, charindex('\', reverse(@backup_file_path)) -1) -- still has the .bak extension /* DEBUG */ print @db_name set @db_name = left(@db_name, charindex('.', @db_name) -1) /* DEBUG */ print @db_name set @db_name = lower(@db_name) /* DEBUG */ print @db_name -- step 2b: find out the logical names of the mdf and ldf files declare @mdf_logical_name varchar(100), @ldf_logical_name varchar(100) declare @backup_file_contents table ( LogicalName nvarchar(128), PhysicalName nvarchar(260), [Type] char(1), FileGroupName nvarchar(128), [Size] numeric(20,0), [MaxSize] numeric(20,0), FileID bigint, CreateLSN numeric(25,0), DropLSN numeric(25,0) NULL, UniqueID uniqueidentifier, ReadOnlyLSN numeric(25,0) NULL, ReadWriteLSN numeric(25,0) NULL, BackupSizeInBytes bigint, SourceBlockSize int, FileGroupID int, LogGroupGUID uniqueidentifier NULL, DifferentialBaseLSN numeric(25,0) NULL, DifferentialBaseGUID uniqueidentifier, IsReadOnly bit, IsPresent bit ) insert into @backup_file_contents exec ('restore filelistonly from disk=' + '''' + @backup_file_path + '''') select @mdf_logical_name = LogicalName from @backup_file_contents where [Type] = 'D' select @ldf_logical_name = LogicalName from @backup_file_contents where [Type] = 'L' /* DEBUG */ print @mdf_logical_name + ', ' + @ldf_logical_name -- step 2c: restore declare @mdf_file_name varchar(1000), @ldf_file_name varchar(1000) set @mdf_file_name = @restore_directory + @db_name + '.mdf' set @ldf_file_name = @restore_directory + @db_name + '.ldf' /* DEBUG */ print 'mdf_logical_name = ' + @mdf_logical_name + '|' + 'ldf_logical_name = ' + @ldf_logical_name + '|' + 'db_name = ' + @db_name + '|' + 'backup_file_path = ' + @backup_file_path + '|' + 'restore_directory = ' + @restore_directory + '|' + 'mdf_file_name = ' + @mdf_file_name + '|' + 'ldf_file_name = ' + @ldf_file_name restore database @db_name from disk = @backup_file_path with move @mdf_logical_name to @mdf_file_name, move @ldf_logical_name to @ldf_file_name -- step 2d: iterate set @index = @index + 1 end close backup_file_cursor deallocate backup_file_cursor -- end try -- begin catch -- print error_message() -- rollback transaction -- return -- end catch -- -- commit transaction end Does anybody have any ideas why this might be happening? Another question: is the transaction code useful ? i.e., if there are 2 databases to be restored, will SQL Server undo the restore of one database if the second restore fails?

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  • Variable mysteriously changing value

    - by Eitan
    I am making a simple tcp/ip chat program for practicing threads and tcp/ip. I was using asynchronous methods but had a problem with concurrency so I went to threads and blocking methods (not asynchronous). I have two private variables defined in the class, not static: string amessage = string.Empty; int MessageLength; and a Thread private Thread BeginRead; Ok so I call a function called Listen ONCE when the client starts: public virtual void Listen(int byteLength) { var state = new StateObject {Buffer = new byte[byteLength]}; BeginRead = new Thread(ReadThread); BeginRead.Start(state); } and finally the function to receive commands and process them, I'm going to shorten it because it is really long: private void ReadThread(object objectState) { var state = (StateObject)objectState; int byteLength = state.Buffer.Length; while (true) { var buffer = new byte[byteLength]; int len = MySocket.Receive(buffer); if (len <= 0) return; string content = Encoding.ASCII.GetString(buffer, 0, len); amessage += cleanMessage.Substring(0, MessageLength); if (OnRead != null) { var e = new CommandEventArgs(amessage); OnRead(this, e); } } } Now, as I understand it only one thread at a time will enter BeginRead, I call Receive, it blocks until I get data, and then I process it. The problem: the variable amessage will change it's value between statements that do not touch or alter the variable at all, for example at the bottom of the function at: if (OnRead != null) "amessage" will be equal to 'asdf' and at if (OnRead != null) "amessage" will be equal to qwert. As I understand it this is indicative of another thread changing the value/running asynchronously. I only spawn one thread to do the receiving and the Receive function is blocking, how could there be two threads in this function and if there is only one thread how does amessage's value change between statements that don't affect it's value. As a side note sorry for spamming the site with these questions but I'm just getting a hang of this threading story and it's making me want to sip cyanide. Thanks in advance. EDIT: Here is my code that calls the Listen Method in the client: public void ConnectClient(string ip,int port) { client.Connect(ip,port); client.Listen(5); } and in the server: private void Accept(IAsyncResult result) { var client = new AbstractClient(MySocket.EndAccept(result)); var e = new CommandEventArgs(client, null); Clients.Add(client); client.Listen(5); if (OnClientAdded != null) { var target = (Control) OnClientAdded.Target; if (target != null && target.InvokeRequired) target.Invoke(OnClientAdded, this, e); else OnClientAdded(this, e); } client.OnRead += OnRead; MySocket.BeginAccept(new AsyncCallback(Accept), null); } All this code is in a class called AbstractClient. The client inherits the Abstract client and when the server accepts a socket it create's it's own local AbstractClient, in this case both modules access the functions above however they are different instances and I couldn't imagine threads from different instances combining especially as no variable is static.

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  • Does JavaME and/or Proguard reorder assignments?

    - by chrisdew
    This is a simplified example - I have two threads: Can JavaME and/Proguard ever reorder the obX = ... statements, such that thread_B will have a null pointer exception at ob2.someMethod? thread_A: Object ob1 = null; Object ob2 = null; ... ob1 = something1; ob2 = something2; thread_B: if (ob2 != null) { ob1.someMethod(); ... } P.S. I do realise that synchronising these will avoid the issue. Synchronisation has both a performance overhead, and more importantly, a chance to introduce deadlock.

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  • Can't get recursive function to work in Java

    - by Ahmed Salah
    I read docs about java recorsion and I thought I have understood it, but when I try to use it in the following example, it does not work as expected. I a class account, which has amount and can have forther subAccount. I would have implemented one method getSum, which has to return the summ of the amount of the account and amount of all of its subaccount. In the following code, the call of the method getSumm() should return 550, but it behaves strange. can somebody help please? public class Balance{ ArrayList<Balance> subAccounts = new ArrayList<Balance>(); String accountID = null; Double amount = null; double result=0; public double getSum(ArrayList<Balance> subAccounts){ if(subAccounts !=null && subAccounts.size()>0){ for (int i = 0; i < subAccounts.size(); i++) { result = result + getSum(subAccounts.get(i).subAccounts); } } else { return amount; } return result; } public static void main(String[] args) { Balance bs1 = new Balance(); Balance bs2 = new Balance(); Balance bs3 = new Balance(); bs1.amount=100.0; bs2.amount=150.0; bs3.amount=300.0; ArrayList<Balance> subAccounts1 = new ArrayList<Balance>(); bs2.subAccounts=null; bs3.subAccounts=null; subAccounts1.add(bs2); subAccounts1.add(bs3); bs1.subAccounts=subAccounts1; double sum= bs1.getSum(subAccounts1); System.out.println(sum); } }

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  • Problem with migrating a model in ruby

    - by Shreyas Satish
    I run script/generate model query edit query.rb in models.. class Query < ActiveRecord::Base #I even tried Migrations instead of Base def sef.up create table :queries do|t| t.string :name end end def self.down drop_table :queries end end ,run rake db:migrate. and what I see in db is this: mysql> desc queries; +------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+----------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | created_at | datetime | YES | | NULL | | | updated_at | datetime | YES | | NULL | | +------------+----------+------+-----+---------+----------------+ Where is the "name" field? HELP ! Cheers !

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  • Parallel Classloading Revisited: Fully Concurrent Loading

    - by davidholmes
    Java 7 introduced support for parallel classloading. A description of that project and its goals can be found here: http://openjdk.java.net/groups/core-libs/ClassLoaderProposal.html The solution for parallel classloading was to add to each class loader a ConcurrentHashMap, referenced through a new field, parallelLockMap. This contains a mapping from class names to Objects to use as a classloading lock for that class name. This was then used in the following way: protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { synchronized (getClassLoadingLock(name)) { // First, check if the class has already been loaded Class c = findLoadedClass(name); if (c == null) { long t0 = System.nanoTime(); try { if (parent != null) { c = parent.loadClass(name, false); } else { c = findBootstrapClassOrNull(name); } } catch (ClassNotFoundException e) { // ClassNotFoundException thrown if class not found // from the non-null parent class loader } if (c == null) { // If still not found, then invoke findClass in order // to find the class. long t1 = System.nanoTime(); c = findClass(name); // this is the defining class loader; record the stats sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0); sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1); sun.misc.PerfCounter.getFindClasses().increment(); } } if (resolve) { resolveClass(c); } return c; } } Where getClassLoadingLock simply does: protected Object getClassLoadingLock(String className) { Object lock = this; if (parallelLockMap != null) { Object newLock = new Object(); lock = parallelLockMap.putIfAbsent(className, newLock); if (lock == null) { lock = newLock; } } return lock; } This approach is very inefficient in terms of the space used per map and the number of maps. First, there is a map per-classloader. As per the code above under normal delegation the current classloader creates and acquires a lock for the given class, checks if it is already loaded, then asks its parent to load it; the parent in turn creates another lock in its own map, checks if the class is already loaded and then delegates to its parent and so on till the boot loader is invoked for which there is no map and no lock. So even in the simplest of applications, you will have two maps (in the system and extensions loaders) for every class that has to be loaded transitively from the application's main class. If you knew before hand which loader would actually load the class the locking would only need to be performed in that loader. As it stands the locking is completely unnecessary for all classes loaded by the boot loader. Secondly, once loading has completed and findClass will return the class, the lock and the map entry is completely unnecessary. But as it stands, the lock objects and their associated entries are never removed from the map. It is worth understanding exactly what the locking is intended to achieve, as this will help us understand potential remedies to the above inefficiencies. Given this is the support for parallel classloading, the class loader itself is unlikely to need to guard against concurrent load attempts - and if that were not the case it is likely that the classloader would need a different means to protect itself rather than a lock per class. Ultimately when a class file is located and the class has to be loaded, defineClass is called which calls into the VM - the VM does not require any locking at the Java level and uses its own mutexes for guarding its internal data structures (such as the system dictionary). The classloader locking is primarily needed to address the following situation: if two threads attempt to load the same class, one will initiate the request through the appropriate loader and eventually cause defineClass to be invoked. Meanwhile the second attempt will block trying to acquire the lock. Once the class is loaded the first thread will release the lock, allowing the second to acquire it. The second thread then sees that the class has now been loaded and will return that class. Neither thread can tell which did the loading and they both continue successfully. Consider if no lock was acquired in the classloader. Both threads will eventually locate the file for the class, read in the bytecodes and call defineClass to actually load the class. In this case the first to call defineClass will succeed, while the second will encounter an exception due to an attempted redefinition of an existing class. It is solely for this error condition that the lock has to be used. (Note that parallel capable classloaders should not need to be doing old deadlock-avoidance tricks like doing a wait() on the lock object\!). There are a number of obvious things we can try to solve this problem and they basically take three forms: Remove the need for locking. This might be achieved by having a new version of defineClass which acts like defineClassIfNotPresent - simply returning an existing Class rather than triggering an exception. Increase the coarseness of locking to reduce the number of lock objects and/or maps. For example, using a single shared lockMap instead of a per-loader lockMap. Reduce the lifetime of lock objects so that entries are removed from the map when no longer needed (eg remove after loading, use weak references to the lock objects and cleanup the map periodically). There are pros and cons to each of these approaches. Unfortunately a significant "con" is that the API introduced in Java 7 to support parallel classloading has essentially mandated that these locks do in fact exist, and they are accessible to the application code (indirectly through the classloader if it exposes them - which a custom loader might do - and regardless they are accessible to custom classloaders). So while we can reason that we could do parallel classloading with no locking, we can not implement this without breaking the specification for parallel classloading that was put in place for Java 7. Similarly we might reason that we can remove a mapping (and the lock object) because the class is already loaded, but this would again violate the specification because it can be reasoned that the following assertion should hold true: Object lock1 = loader.getClassLoadingLock(name); loader.loadClass(name); Object lock2 = loader.getClassLoadingLock(name); assert lock1 == lock2; Without modifying the specification, or at least doing some creative wordsmithing on it, options 1 and 3 are precluded. Even then there are caveats, for example if findLoadedClass is not atomic with respect to defineClass, then you can have concurrent calls to findLoadedClass from different threads and that could be expensive (this is also an argument against moving findLoadedClass outside the locked region - it may speed up the common case where the class is already loaded, but the cost of re-executing after acquiring the lock could be prohibitive. Even option 2 might need some wordsmithing on the specification because the specification for getClassLoadingLock states "returns a dedicated object associated with the specified class name". The question is, what does "dedicated" mean here? Does it mean unique in the sense that the returned object is only associated with the given class in the current loader? Or can the object actually guard loading of multiple classes, possibly across different class loaders? So it seems that changing the specification will be inevitable if we wish to do something here. In which case lets go for something that more cleanly defines what we want to be doing: fully concurrent class-loading. Note: defineClassIfNotPresent is already implemented in the VM as find_or_define_class. It is only used if the AllowParallelDefineClass flag is set. This gives us an easy hook into existing VM mechanics. Proposal: Fully Concurrent ClassLoaders The proposal is that we expand on the notion of a parallel capable class loader and define a "fully concurrent parallel capable class loader" or fully concurrent loader, for short. A fully concurrent loader uses no synchronization in loadClass and the VM uses the "parallel define class" mechanism. For a fully concurrent loader getClassLoadingLock() can return null (or perhaps not - it doesn't matter as we won't use the result anyway). At present we have not made any changes to this method. All the parallel capable JDK classloaders become fully concurrent loaders. This doesn't require any code re-design as none of the mechanisms implemented rely on the per-name locking provided by the parallelLockMap. This seems to give us a path to remove all locking at the Java level during classloading, while retaining full compatibility with Java 7 parallel capable loaders. Fully concurrent loaders will still encounter the performance penalty associated with concurrent attempts to find and prepare a class's bytecode for definition by the VM. What this penalty is depends on the number of concurrent load attempts possible (a function of the number of threads and the application logic, and dependent on the number of processors), and the costs associated with finding and preparing the bytecodes. This obviously has to be measured across a range of applications. Preliminary webrevs: http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.hotspot/ http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.jdk/ Please direct all comments to the mailing list [email protected].

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  • Good practices for intialising properties ?

    - by Rubans
    HI, I have a class property that is a list of strings, List. Sometimes this property is null or if it has been set but the list is empty then count is 0. However elsewhere in my code I need to check whether this property is set, so currently my code check whether it's null and count is 0 which seems messy. if(objectA.folders is null) { if(objectA.folders.count == 0) { // do something } } Any recommendation on how this should be handled? Maybe I should always initialise the property so that it's never null? Appolgies if this is a silly question.

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  • How do I apply a "template" or "skeleton" of code in C# here?

    - by Scott Stafford
    In my business layer, I need many, many methods that follow the pattern: public BusinessClass PropertyName { get { if (this.m_LocallyCachedValue == null) { if (this.Record == null) { this.m_LocallyCachedValue = new BusinessClass( this.Database, this.PropertyId); } else { this.m_LocallyCachedValue = new BusinessClass( this.Database, this.Record.ForeignKeyName); } } return this.m_LocallyCachedValue; } } I am still learning C#, and I'm trying to figure out the best way to write this pattern once and add methods to each business layer class that follow this pattern with the proper types and variable names substituted. BusinessClass is a typename that must be substituted, and PropertyName, PropertyId, ForeignKeyName, and m_LocallyCachedValue are all variables that should be substituted for. Are attributes usable here? Do I need reflection? How do I write the skeleton I provided in one place and then just write a line or two containing the substitution parameters and get the pattern to propagate itself? EDIT: Modified my misleading title -- I am hoping to find a solution that doesn't involve code generation or copy/paste techniques, and rather to be able to write the skeleton of the code once in a base class in some form and have it be "instantiated" into lots of subclasses as the accessor for various properties. EDIT: Here is my solution, as suggested but left unimplemented by the chosen answerer. // I'll write many of these... public BusinessClass PropertyName { get { return GetSingleRelation(ref this.m_LocallyCachedValue, this.PropertyId, "ForeignKeyName"); } } // That all call this. public TBusinessClass GetSingleRelation<TBusinessClass>( ref TBusinessClass cachedField, int fieldId, string contextFieldName) { if (cachedField == null) { if (this.Record == null) { ConstructorInfo ci = typeof(TBusinessClass).GetConstructor( new Type[] { this.Database.GetType(), typeof(int) }); cachedField = (TBusinessClass)ci.Invoke( new object[] { this.Database, fieldId }); } else { var obj = this.Record.GetType().GetProperty(objName).GetValue( this.Record, null); ConstructorInfo ci = typeof(TBusinessClass).GetConstructor( new Type[] { this.Database.GetType(), obj.GetType()}); cachedField = (TBusinessClass)ci.Invoke( new object[] { this.Database, obj }); } } return cachedField; }

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  • jQuery JSON .each problem

    - by Aran
    I have a JSON object that looks like this. [ { "id" : "23", "event_id" : "0", "sport_title" : null, "event_title" : null, "title" : "Under 1 day!", "content" : "It\\'s all hotting up and battle commences in under one day!", "link" : "" }, { "id" : "20", "event_id" : "0", "sport_title" : null, "event_title" : null, "title" : "Getting Exciting", "content" : "Less than two days till it all kicks off, with cricket....", "link" : "" }] and I am trying to get the details out of this JSON Object and prepend them to a <ul> the code that I am currently trying looks like this and is having problems var writeup_list = writeuplist; $.getJSON('../json/getWriteups.json', function(data) { $.each(data.items, function(i, item) { writeup_list.html(function() { var output; output = '<li><a href="/writeups/index.php#writeup_' + item.id + '">'; if(item.sport_title != null) { output += item.sport_title + ' - '; } output += item.title + '</a></li>'; return output; }); }); }); writeuplist is just the ul object. I am also worried about overriding information that is already in the list or just adding again. Don't want to keep adding the same data. What is a good way to avoid this? I seem to be having a problem in getting the data out of the JSON file I believe it has something to do with the way am trying to access it in the .each function. Can anyone spot where am going wrong?

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  • Repaint window problems

    - by nXqd
    #include "stdafx.h" // Mario Headers #include "GameMain.h" #define MAX_LOADSTRING 100 // Global Variables: HINSTANCE hInst; // current instance TCHAR szTitle[MAX_LOADSTRING]; // The title bar text TCHAR szWindowClass[MAX_LOADSTRING]; // the main window class name // Mario global variables ================= CGameMain* gGameMain; HWND hWnd; PAINTSTRUCT ps; // ======================================== // Forward declarations of functions included in this code module: ATOM MyRegisterClass(HINSTANCE hInstance); BOOL InitInstance(HINSTANCE, int); LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); INT_PTR CALLBACK About(HWND, UINT, WPARAM, LPARAM); // My unprocess function ===================================== void OnCreate(HWND hWnd) { } void OnKeyUp(WPARAM wParam) { switch (wParam) { case VK_LEFT: gGameMain->KeyReleased(LEFT); break; case VK_UP: gGameMain->KeyReleased(UP); break; case VK_RIGHT: gGameMain->KeyReleased(RIGHT); break; case VK_DOWN: gGameMain->KeyReleased(DOWN); break; } } void OnKeyDown(HWND hWnd,WPARAM wParam) { switch (wParam) { case VK_LEFT: gGameMain->KeyPressed(LEFT); break; case VK_UP: gGameMain->KeyPressed(UP); break; case VK_RIGHT: gGameMain->KeyPressed(RIGHT); break; case VK_DOWN: gGameMain->KeyPressed(DOWN); break; } } void OnPaint(HWND hWnd) { HDC hdc = BeginPaint(hWnd,&ps); RECT rect; GetClientRect(hWnd,&rect); HDC hdcDouble = CreateCompatibleDC(hdc); HBITMAP hdcBitmap = CreateCompatibleBitmap(hdc,rect.right,rect.bottom); HBITMAP bmOld = (HBITMAP)SelectObject(hdcDouble, hdcBitmap); gGameMain->SetHDC(&hdcDouble); gGameMain->SendMessage(MESSAGE_PAINT); BitBlt(hdc,0,0,rect.right,rect.bottom,hdcDouble,0,0,SRCCOPY); SelectObject(hdcDouble,bmOld); DeleteDC(hdcDouble); DeleteObject(hdcBitmap); DeleteDC(hdc); } void OnDestroy() { gGameMain->isPlaying = false; EndPaint(hWnd,&ps); } // My unprocess function ===================================== ATOM MyRegisterClass(HINSTANCE hInstance) { WNDCLASSEX wcex; wcex.cbSize = sizeof(WNDCLASSEX); wcex.style = CS_HREDRAW | CS_VREDRAW; wcex.lpfnWndProc = WndProc; wcex.cbClsExtra = 0; wcex.cbWndExtra = 0; wcex.hInstance = hInstance; wcex.hIcon = LoadIcon(hInstance, MAKEINTRESOURCE(IDI_GDIMARIO)); wcex.hCursor = LoadCursor(NULL, IDC_ARROW); wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1); wcex.lpszMenuName = MAKEINTRESOURCE(IDC_GDIMARIO); wcex.lpszClassName = szWindowClass; wcex.hIconSm = LoadIcon(wcex.hInstance, MAKEINTRESOURCE(IDI_SMALL)); return RegisterClassEx(&wcex); } BOOL InitInstance(HINSTANCE hInstance, int nCmdShow) { hInst = hInstance; // Store instance handle in our global variable hWnd = CreateWindow(szWindowClass, szTitle, WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, WIDTH, HEIGHT, 0, NULL, hInstance, NULL); if (!hWnd) { return FALSE; } // ---------------- Start gdiplus ------------------ GdiplusStartup(&gdiToken,&gdiStartInput,NULL); // ------------------------------------------------- // Init GameMain gGameMain = new CGameMain(); ShowWindow(hWnd, nCmdShow); UpdateWindow(hWnd); return TRUE; } LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam) { int wmId, wmEvent; switch (message) { case WM_COMMAND: wmId = LOWORD(wParam); wmEvent = HIWORD(wParam); // Parse the menu selections: switch (wmId) { case IDM_ABOUT: DialogBox(hInst, MAKEINTRESOURCE(IDD_ABOUTBOX), hWnd, About); break; case IDM_EXIT: DestroyWindow(hWnd); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } break; case WM_KEYDOWN: OnKeyDown(hWnd,wParam); break; case WM_KEYUP: OnKeyUp(wParam); break; case WM_CREATE: OnCreate(hWnd); break; case WM_PAINT: OnPaint(hWnd); break; case WM_DESTROY: OnDestroy(); PostQuitMessage(0); break; default: return DefWindowProc(hWnd, message, wParam, lParam); } return 0; } // Message handler for about box. INT_PTR CALLBACK About(HWND hDlg, UINT message, WPARAM wParam, LPARAM lParam) { UNREFERENCED_PARAMETER(lParam); switch (message) { case WM_INITDIALOG: return (INT_PTR)TRUE; case WM_COMMAND: if (LOWORD(wParam) == IDOK || LOWORD(wParam) == IDCANCEL) { EndDialog(hDlg, LOWORD(wParam)); return (INT_PTR)TRUE; } break; } return (INT_PTR)FALSE; } int APIENTRY _tWinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPTSTR lpCmdLine,int nCmdShow) { UNREFERENCED_PARAMETER(hPrevInstance); UNREFERENCED_PARAMETER(lpCmdLine); // TODO: Place code here. MSG msg; HACCEL hAccelTable; // Initialize global strings LoadString(hInstance, IDS_APP_TITLE, szTitle, MAX_LOADSTRING); LoadString(hInstance, IDC_GDIMARIO, szWindowClass, MAX_LOADSTRING); MyRegisterClass(hInstance); // Perform application initialization: if (!InitInstance (hInstance, nCmdShow)) { return FALSE; } hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_GDIMARIO)); // Main message loop: // GameLoop PeekMessage(&msg,NULL,0,0,PM_NOREMOVE); while (gGameMain->isPlaying) { while (PeekMessage(&msg,NULL,0,0,PM_REMOVE)) { if (msg.message == WM_QUIT) break; TranslateMessage(&msg); DispatchMessage(&msg); } if (gGameMain->enterNextState) { gGameMain->SendMessage(MESSAGE_ENTER); gGameMain->enterNextState = false; } gGameMain->SendMessage(MESSAGE_UPDATE); InvalidateRect(hWnd,NULL,FALSE); /*if (gGameMain->exitCurrentState) { gGameMain->SendMessage(MESSAGE_EXIT); gGameMain->enterNextState = true; gGameMain->exitCurrentState = false; }*/ ::Sleep(gGameMain->timer); // Do your game stuff here } GdiplusShutdown(gdiToken); // Shut down gdiplus token return (int) msg.wParam; } I use InvalidateRect(hWnd,NULL,FALSE); for repaint window, but the problem I met is when I repaint without any changes in Game struct . First it paints my logo well, the second time ( just call InvalidateRect(hWnd,NULL,FALSE); without gGameMain-SendMessage(MESSAGE_ENTER); which is init some variables for painting . Thanks for reading this :)

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