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How do i know when a lambda expression is null

I need to programatically check whether a nested property/function result in a lambda expression is null or not. The problem is that the null could be in any of the nested subproperties. Example. Function is: public static bool HasNull<T, Y>(this T someType, Expression<Func<T, Y>> input) { //Determine if expression has a nul...

Entity Framework - MySQL - Null Comparison!

Whats wrong with following code? :( int? parentFolderId = null; if( this.Request.QueryString ["folderId"] != null ) parentFolderId = Convert.ToInt32( this.Request.QueryString ["folderId"] ); f = ( from x in this.EntityDataContext.folders where x.parent_id == parentFolderId select x ).ToList(); It returns nothing! Though there ARE...

How can i tell if a MySQL query returned nothing in PHP?

Question title says it all. I'm using PHP5 and MySQL. EDIT: I'm using mysql_...() functions. ...

json_encode is returning null?

For some reason the item "description" returns null with the following code: <?php include('db.php'); $result = mysql_query('SELECT * FROM `staff` ORDER BY `id` DESC LIMIT 2') or die(mysql_error()); $rows = array(); while($row = mysql_fetch_assoc($result)){ $rows[] = $row; } echo json_encode($rows); ?> Here is the schema for my ...

Can a cast a nullable column to a NOT NULL column?

In SQL 2005/8 I'm looking to convert a column in select query to a NOT NULL column. coalease() and isnull(), although fine functions, is not what I'm looking for. I want the select to throw an error is any of the data is NULL. Is this possible? [Update] Clearly the best approach would be to modify the source table, unfortunatly in th...

MS Access: How to replace blank (null ) values with 0 for all records?

MS Access: How to replace blank (null ) values with 0 for all records? I guess it has to be done using SQL. I can use Find and Replace to replace 0 with blank, but not the other way around (won't "find" a blank, even if I enter [Ctrl-Spacebar] which inserts a space. So I guess I need to do SQL where I find null values for MyField, then...

Will isset() return false if I assign NULL to a variable?

I mean... I "set" it to NULL. So isset($somethingNULL) == true? ...

NULL in a RubyCocoa application?

Hi, I'm creating an application in RubyCocoa and I have this code: fileContents = OSX::NSAttributedString.alloc.initWithData_options_documentAttributes_error_(data, null, null, outError) It gives me this error: 2009-12-31 19:42:54.317 Ruby Text[3791:a0f] MyDocument#readFromData_ofType_error_: OSX::OCMessageSendException: Can't get O...

null comparison, prefix increment, properties, Length properties of struct in C#

Hi everyone, I have some questions in C# what are the differences between null comparisons null == value and value == null (value is a variable of any kind: int, string, float,...) I heard that using prefix increment ++i instead of i++ in some case will enhance the program performance. Why is it so? I have a snippet code as follow: ...

Array of pointers member, is it initialized?

If I have a class A { private: Widget* widgets[5]; }; Is it guaranteed that all pointers are NULL, or do I need to initialize them in the constructor? Is it true for all compilers? Thanks. ...

Possible to pass null from Powershell to a .Net API that expects a string?

API: namespace ClassLibrary1 { public class Class1 { public static string Test(string input) { if (input == null) return "It's null"; if (input == string.Empty) return "It's empty"; else return "Non-empty string of length " + inpu...

javascript validation- rbColorId object is still detected...

function submitcheck() { var f = document.form1; if (f.rbTemplate!= null) { ... alert('Please choose template'); return false; ... } if (f.rbColorId!= null) { ... alert('Please choose template color'); return false; ... } } function ShowColor() { var f= document.form1; ...

Objective-C: NSLog prints (null) for a var assigned to nil?

I'm curious why a variable overtly assigned to nil, prints as (null) with NSLog: NSString *myVar = nil; NSLog(@"%@", myVar); # RESULT: ' (null) ' This is of course quite confusing given all the different kinds of "nothingness" to figure out in Objective-C, and had me trying to test various IF NULL syntaxes. ...

Why does a reference type is not initialized to null ?

Check this code.. string str; if (str.Contains("something..")) { } Compiler throws this error for this code Use of unassigned local variable 'str' Why does a reference type is not initialized to null ? Just want to know out of curiosity. I'd also want to know what happens for code below. how does this assignme...

Null pattern in Python underused?

Every now and then I come across code like this: foo = Foo() ... if foo.bar is not None and foo.bar.baz == 42: shiny_happy(...) Which seems, well, unpythonic, to me. In Objective-C, you can send messages to nil and get nil as the answer. I've always thought that's quite handy. Of course it is possible to implement a Null pattern i...

Best way to check if column returns a null value (from database to .net application)

I have a table with a DateTime column the column can have NULL values Now I connect to the database using an ODBC connection and get the value into a DataTable in .net / c#. I am able to check it for NULL by going if(String.IsNullOrEmpty(table.rows[0][0].ToString()) { //Whatever I want to do } Is String.IsNullOrEmpty the correc...

Can I avoid to overwrite a column with a NULL value on INSERT query?

I have two different queries in my php page for the same table, the first one is executed if I have two different values for two columns, but in some case, i can use only the first value, can I do it with the same query or should I use two different queries? // query 1 "INSERT INTO my_table (column_1, column_2) VALUES ('$value_1', '$val...

Comparing structs to null

Possible Duplicate: C# okay with comparing value types to null I was working on a windows app in a multithreaded environment and would sometimes get the exception "Invoke or BeginInvoke cannot be called on a control until the window handle has been created." So I figured that I'd just add this line of code: if(this.Handle != nu...

Update Procedure "N/A" to Empty String on MS Access

Hello, I currently have a table in MS Access called Total Registrants. How can I insert string "N/A" into the cells of the column "EventRegCompany" where there are blank cells? I created an update query UPDATE Test SET Test.eventRegCompany = "N/A" WHERE (((Test.eventRegCompany)=NULL)); Thanks! ...

What's the impact of NULL on MySQL tables? (InnoDB)

Hello guys, Recently, I've been thinking if it's worth to have 1 table with perhaps a lot of NULL columns or if it's better to have more tables with no NULLs. I've heard that NULL isn't stored on InnoDB, so I was wondering if there is any downside or problem with having a bunch of rows with a lot of NULLs. I have always heard that commo...