Is there an easy way to terminate the running of a linqpad query based on some parameter?
For example
int x = someValueThatCouldBeNull;
if(x == null)
{
//terminate the query
}
else
{
x.Dump();
}
Related
in store procedure we can check record is exist or not using following query for fast performance
if EXISTS ( Select 1 from Table_Name where id=#id )
But what about Linq query.
right now i have to store whole data in object like this
UserDetail _U=db.UserDetails.where(x=>x.id==1).FirstOrDefault();
Any Solution?
Use Linq's Any ie bool exist = db.UserDetails.Any(x => x.id == 1);
if(db.UserDetails.Any(x => x.id == 1)) {
var userDetail = db.UserDetails.FirstOrDefault(x => x.id == 1);
}
bool exist = db.UserDetails.Where(x=>x.id==1).Any();
if(exist){
//your-code
}else{
//your-code
}
Just check
if(_U == null)
This way you will get what you want in single query and you not need to execute addition query like
db.UserDetails.Any(x => x.id == 1)
I think, it does not require to fire two query. It can be accomplish by single query.
UserDetails objUserDetails =db.UserDetails.FirstOrDefault(x => x.id == 1);
if(objUserDetails==null)
{
// Do something
}
else
{
// do something with objUserDetails
}
var qry = db.User_Detail.Where(x => x.User_Id == 1).FirstOrDefault();
if(qry !=null)
{
// Do something
}
else
{
return false;
}
Try This...
My website went down for a few days, therefore I am trying to produce some error handling while the MVC app doesnt have access to certain resources so if something doesnt become unavailable again the WHOLE THING doesnt have to go down.
At the moment a controller is trying to access viewbag.moreNewProducts that isnt available.
public ActionResult Index(string search)
{
string[] newProductLines = this.getMoreNewProducts();
string[] newNews = this.getMoreNews();
string[] newPromotions = this.getMorePromotions();
string[] fewerProductLines = this.getLessNewProducts(newProductLines);
ViewBag.moreNewProducts = newProductLines;
ViewBag.moreNews = newNews;
ViewBag.morePromotions = newPromotions;
ViewBag.lessNewProducts = fewerProductLines;
bool disableShowMore = false;
This is where I run into an error: " foreach (string line in newProductLines)"
public string[] getLessNewProducts(string[] newProductLines)
{
int charCount = 0;
int arrayCount = 0;
string[] displayProductLines = new string[6];
bool continueWriting;
if (newProductLines == null)
{
foreach (string line in newProductLines)
{
continueWriting = false;
for (int i = 0; charCount < 250 && i < line.Length && arrayCount < 5; i++)
{
string index = newProductLines[arrayCount].Substring(i, 1);
displayProductLines[arrayCount] += index;
charCount++;
continueWriting = true;
}
if (continueWriting == true)
{
arrayCount++;
}
}
string[] LessNewProducts = new string[arrayCount];
for (int d = 0; d < arrayCount; d++)
{
LessNewProducts[d] = displayProductLines[d];
}
return LessNewProducts;
}
else
{
return null;
}
}
how do I get around an if else statement so the whole thing doesnt have to crash?
Two things.
Your if (newProductLines == null) statement has the wrong condition on it. I don't believe that you want to enter that if newProductLines is null. You can inverse this condition to get the desired result(if (newProductLines != null)).
If you run into another situation later where you need to catch an error, you can always use the try-catch block to catch exceptions that you are expecting.
try
{
//code that could cause the error here
}
catch(NullReferenceException nullRefExcep)
{
//what you want it to do if the null reference exception occurs
}
if (newProductLines == null)
should be replaced with if (newProductLines != null) so you don't have to handle the code with newProductLines as null. Basically, with this condition you will always have the NullReferenceException unless you manage your exception with a try catch block.
The real question to ask yourself is:
Why would newProductLines be null?
Presumably getMoreNewProducts() found a situation where it thought it would be appropriate to return a null value.
If this is happening because the system has an error that would make your page meaningless, then you may just want to change getMoreNewProducts() so that it throws an exception when that error state occurs. Typically it's safest and easiest to debug programs that fail as soon as they run into an unexpected situation.
If this is happening because there are no new products, then you should just return an empty collection, rather than null. All your code should work just fine after that, without the need for an if/else statement: it will return an empty array for LessNewProducts, which is probably correct.
However, let's assume that there's a situation that you're anticipating will occur from time to time, which will make it impossible for you to retrieve newProductLines at that time, but which you would like the system to handle gracefully otherwise. You could just use null to indicate that the value isn't there, but it's really hard to know which variables might be null and which never should be. It may be wiser to use an optional type to represent that getMoreNewProducts() might not return anything at all, so you can force any consuming code to recognize this possibility and figure out how to deal with it before the project will even compile:
public ActionResult Index(string search)
{
Maybe<string[]> newProductLines = this.getMoreNewProducts();
string[] newNews = this.getMoreNews();
string[] newPromotions = this.getMorePromotions();
Maybe<string[]> fewerProductLines = newProductLines.Select(this.getLessNewProducts);
Disclaimer: I am the author of the Maybe<> class referenced above.
Here are some additional improvements I'd suggest:
Don't use ViewBag. Instead, create a strongly-typed ViewModel so that you can catch errors in your code at compile-time more often:
var viewModel = new ReportModel {
newProductLines = this.getMoreNewProducts(),
newNews = this.getMoreNews(),
...
};
...
return View(viewModel);
Learn to use LINQ. It will simplify a lot of your very complicated code. For example, instead of:
string[] LessNewProducts = new string[arrayCount];
for (int d = 0; d < arrayCount; d++)
{
LessNewProducts[d] = displayProductLines[d];
}
return LessNewProducts;
... you can say:
string[] LessNewProducts = displayProductLines.Take(arrayCount).ToArray();
In fact, I think your entire getLessNewProducts() method can be replaced with this:
return newProductLines
.Where(line => line.Length > 0)
.Select(line => line.Substring(0, Math.Min(line.Length, 250)))
.Take(5);
We have a stored procedure that returns several tables. When calling it using NHibernate, we use the bean transformer but only get the first table transformed and all other results are ignored.
I know that NH is able to process several queries in one db trip using futures but we only have one query and it produces a result that is similar to what we would get with futures, but getting this from a stored procedure.
I believe this scenario is quite common but could not find any clues. Is it possible to use NH to retrieve such results?
Yes,you can use MultiQuery "Hack" like this:
The procudure:
CREATE PROCEDURE [dbo].[proc_Name]
AS BEGIN
SELECT * FROM Question
SELECT * FROM Question
END
The NHibernate Query Code:
public void ProcdureMultiTableQuery()
{
var session = Session;
var procSQLQuery = session.CreateSQLQuery("exec [proc_Name] ?,?");// prcodure returns two table
procSQLQuery.SetParameter(0, userId);
procSQLQuery.SetParameter(1, page);
procSQLQuery.AddEntity(typeof(Question));
var multiResults = session.CreateMultiQuery()
.Add(procSQLQuery)
// More table your procedure returns,more empty SQL query you should add
.Add(session.CreateSQLQuery(" ").AddEntity(typeof(Question))) // the second table returns Question Model
.List();
if (multiResults == null || multiResults.Count == 0)
{
return;
}
if (multiResults.Count != 2)
{
return;
}
var questions1 = ConvertObjectsToArray<Question>((System.Collections.IList)multiResults[0]);
var questions2 = ConvertObjectsToArray<Question>((System.Collections.IList)multiResults[1]);
}
static T[] ConvertObjectsToArray<T>(System.Collections.IList objects)
{
if (objects == null || objects.Count == 0)
{
return null;
}
var array = new T[objects.Count];
for (int i = 0; i < array.Length; i++)
{
array[i] = (T)objects[i];
}
return array;
}
import java.util.Scanner;
public class RPS
{
public void show()
{
int i;
System.out.println("1 - Rock 2 - Paper 3 - Scissor");
Scanner in = new Scanner(System.in);
i = in.nextInt();
double x = Math.random();
int y;
if(x<=0.33)
{
y=1;
}
else if(x>0.33 && x<0.67)
{
y=2;
}
else if(x>=0.67)
{
y=3;
}
for(;;)
{
if(i==y)
System.out.println("It's a draw!");
else if(i==1 && y==2)
System.out.println("Computer wins!");
else if(i==1 && y==3)
System.out.println("You win!");
else if(i==2 && y==1)
System.out.println("You win!");
else if(i==2 && y==3)
System.out.println("Computer wins!");
else if(i==3 && y==1)
System.out.println("Computer wins!");
else if(i==3 && y==2)
System.out.println("You win!");
else
System.out.println("Error!");
}
}
}
Whats wrong?
It gives an error that variable y might not have been intialised in the if's in the for loop.
I have assigned a value to y in the previous if-else section.
so why isnt it getting intialised?
javac is not smart enough to realize that the way your conditions are constructed, one of them will always be true.
You can rewrite your if-statements to make javac realize one branch will always be triggered:
int y;
if(x<=0.33)
{
y=1;
}
else if(x>0.33 && x<0.67)
{
y=2;
}
else // This only triggers when x >= 0.67, so no need to check
{
y=3;
}
Now javac sees that if the first two don't trigger, the last will, so y will always have a value.
You can alternatively add an else branch with an error, in case someone breaks the conditions:
int y;
if(x<=0.33)
{
y=1;
}
else if(x>0.33 && x<0.67)
{
y=2;
}
else if(x >= 0.67)
{
y=3;
}
else
{
// This should never happen
throw new IllegalArgumentException("Something's gone terribly wrong for " + x);
}
This also compiles, and if someone later decides to skew the numbers and turns the first condition into x <= 0.2 but forgets to update the other condition, you'll get an exception at runtime.
I'm trying to write a chess game and find that I cannot find solutions to find a stalemate situation. I'm trying to google, but can't find anything. Is there a well-known algorithm or something?
Your move generator will be one of two different designs;
either it checks for legality while generating the moves
or you generate all possible moves and remove those that are illegal afterwards.
The former is better as it doesn't need post-processing.
A stalemate condition is simply one where there are no legal moves and the moving-side's king is not in check. A checkmate condition is one where there are no legal moves but the moving-side's king is in check.
In other words if you've figured out how to detect check and checkmate, you've already got everything necessary to detect stalemate.
Here is an Open-source code with all the rules for the classic Chess game:
https://github.com/cjortegon/basic-chess
You can run the project right after cloning the project (Android, iOS, Desktop and Web), or you can use the main logic, which is here: https://github.com/cjortegon/basic-chess/tree/master/libgdx/core/src/com/mountainreacher/chess/model
I based my solution on a 3-moments algorithm, first moment is when the player selects a piece from the board, then when the destination of this piece has been chosen and finally when the piece reaches that position (considering that it is an animated game, if not, you can merge step 2 and 3).
The following code has been implemented in Java. From the properties of the model class:
boolean turn;
GenericPiece selected, conquest;
ClassicBoard board;
List<int[]> possibleMovements;
int checkType;
The first method will handle moments 1, 2 and the special 'conquest' moment (applied to pawn piece only):
public boolean onCellClick(int row, int column) {
if (row == -1 && conquest != null) {
checkType = 0;
conquest.changeFigure(column);
return true;
} else if (selected != null) {
if (possibleMovements != null) {
for (int[] move : possibleMovements) {
if (move[0] == row && move[1] == column) {
// Move the PieceActor to the desired position
if (selected.moveTo(row, column)) {
turn = !turn;
}
break;
}
}
}
selected = null;
possibleMovements = null;
return true;
} else {
selected = board.getSelected(turn ? Piece.WHITE_TEAM : Piece.BLACK_TEAM, row, column);
if (selected != null) {
possibleMovements = new ArrayList<>();
possibleMovements.addAll(((GenericPiece) selected).getMoves(board, false));
// Checking the movements
board.checkPossibleMovements(selected, possibleMovements);
if (possibleMovements.size() == 0) {
possibleMovements = null;
selected = null;
return false;
} else {
return true;
}
}
}
return false;
}
And the following method will handle the 3rd moment (when animation finishes):
public void movedPiece(Piece piece) {
Gdx.app.log(TAG, "movedPiece(" + piece.getType() + ")");
// Killing the enemy
Piece killed = board.getSelectedNotInTeam(piece.getTeam(),
piece.getRow(), piece.getColumn());
if (killed != null) {
killed.setAvailable(false);
}
// Checking hacks
GenericPiece[] threat = board.kingIsInDanger();
if (threat != null) {
checkType = board.hasAvailableMoves(threat[0].getTeam()) ? CHECK : CHECK_MATE;
} else {
checkType = NO_CHECK;
}
// Checking castling
if (piece.getFigure() == Piece.ROOK && ((GenericPiece) piece).getMovesCount() == 1) {
Piece king = board.getSelected(piece.getTeam(),
piece.getRow(), piece.getColumn() + 1);
if (king != null && king.getFigure() == Piece.KING && ((GenericPiece) king).getMovesCount() == 0) {
// Left Rook
if (board.getSelected(piece.getRow(), piece.getColumn() - 1) == null) {
king.moveTo(piece.getRow(), piece.getColumn() - 1);
}
} else {
king = board.getSelected(piece.getTeam(),
piece.getRow(), piece.getColumn() - 1);
if (king != null && king.getFigure() == Piece.KING && ((GenericPiece) king).getMovesCount() == 0) {
// Right Rook
if (board.getSelected(piece.getRow(), piece.getColumn() + 1) == null) {
king.moveTo(piece.getRow(), piece.getColumn() + 1);
}
}
}
}
// Conquest
else if (piece.getFigure() == Piece.PAWN && (piece.getRow() == 0 || piece.getRow() == board.getRows() - 1)) {
conquest = (GenericPiece) piece;
checkType = CONQUEST;
}
}
That code covers all the rules from the classic chess, including: regular piece movements, castling, check, check-mate and conquests of pawns.