Here's 14 years worth of jumbled C recipes and notes arranged randomly in a stream of consciousness mode. Some methods are superseded by functionality beyond C 1.

One day I'll organize them into a coherent whole, until them please use "search" in your browser. The other pages in this C series are much better formatted and more informative. You can get Nant, a build tool like the old 'make', from http: Identifiers are the names we give to things like classes, variables, and methods.

In C identifiers must start with an underscore or letter and be composed of letters, numbers and underscores. By convention local variables, arguments passed into methods, and private fields are camelCase. Other identifiers are PascalCase. Reserved keywords like "public", "static" cannot be used for identifiers unless you preface the variable name with " ", e. Here's a list of contextual keywords.

Identifiers can be named these words and the compiler can tell if the word is an identifier or a keyword by its context. A Type has "data members" and "function members", like "int" which contains a value and has methods like "ToString ". C provides built-in, or predefined, types directly in the language which the compiler understands and sets aside key words for them. The value types are: Use "decimal" for money.

These types are aliased into types in the "System" namespace, like "int" being an alias for System. C also provides built-in types in the System namespace like DateTime, although the compiler has no direct knowledge of them. Each object has a pointer to its type. The "GetType " method will return, at runtime, the Type object describing the object. The "typeof" operator will do the same but usually at compile time. Value types mostly built-in types like "int", "double" and custom "struct" and "enum" which have no methods just a value, although with auto-boxing and implied methods it looks they do.

This are stored on the stack. If you need to get the default value, you can use the "default" keyword. You can even use it on generics: Reference types any class, arrays, delegates; anything which is a pointer to a block of memory, these are stored on the heap. If a class does not explicitly call it's parent's constructor with "base", the class's parent's parameterless constructor is called by default if the parent has a parameterless constructor.

This constructor is only called once before the first object of this type is called. Is it guarenteed to be called if no objects of its kind are never created? It can only reference static objects of course and it has no parameters. The above code, oddly enough will print "" for the planes speed, since TopSpeed is not virtual. If we don't set Jet's method to override, we still get "".

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In a subclass you can reuse a variable name, but the compiler will warn you that the subclassed member is "hiding" the parent's variable. If a new variable is really want you want, tell the compiler to stop whining about it by using the "new" modifier not to be confused with the "new" operator. WriteAllText will create the file if it doesn't exist, otherwise overwrites it.

It will also close the file. With files this will close the file. The following code shows that "using" does indeed close the file, otherwise open files would cause problems.

Given an overloaded method, the decision on which method to call is usually made at compile time based on the declared type of the argument.

Even though the "mammal" object is really a Tiger type, the compiler will call the Mammal overload - unless you cast it to a "dynamic" type, in which case it will call the method based on the real type of the object.

Structs are similar to classes, Microsoft calls them 'lightweight' objects. Structs can be more efficient since they do not have to allocate memory in the heap and initialize a real object. Although they can be created with the 'new' operator, structs live on the stack. If you use the "new" operator, all the fields of a struct will be initialized. Without the "new", all the fields must be initialized before the struct may be used.

Structs do not have destructors or finalizers, which kinda makes sense since they have nothing to reclaim except their meager memory footprint in the stack. Many of the built-in types in C are structs.

For example a C "int" is really a. Net type of "System. A C "float" is an alias for "System. If you look at the official docs on "int" you can see it is a struct and implements several interfaces:. Example of using Properties instead of accessor methods. Note the special use of the "value" variable in "set". UtcNow is faster than DateTime. Now since it doesn't have to do the wacky daily savings time calculations.

What's the units for the argument to Sleep? You can make it more implicit by using TimeSpan. The cultural-independent universal format: ToString "u" which prints "yyyy'-'MM'-'dd HH': Since not all characters in strings map to a small friendly byte remember our European friends? C will automatically convert some types for us if the following two conditions are true: The compiler can know the conversion will succeed 2. No information is lost during the conversion.

To sort an array use the static method on Array class.

I don't know why array. In C you can do this with "using" can we create another overload for "using" just to make it more confusing? C provides a special way of disposing of objects after their use - it's the "using" block. The object of the "using" statement must implement the IDisposable interface which contains one member, Dispose. As shown below, after the "using" block is executed, Dispose is immediately called. This tells the compiler that all instances of 'Set' in the rest of the file are references to 'MyUtil.

This would be helpful if 'Set' becomes a real collection class in a future release of. Net and you have coded your own.

Often its convenient to print the state of an object. Instead of overriding the ToString method and explicitly printing each field, you can let C do the work for you with a little bit of Reflection. You could even add code to recursively print the state of the composition objects as well. This is left as an exercise for the student. How to invoke a static method on a dynamic object. This invokes the static method "Get string name " on a "myType" class object and returns an instance of a MyObjectType.

This example shows invoking an instance method on the "this" object, although any other object would work as well as long as you get the methodInfo object from its class. As the following code shows, interfaces can be extended and, unlike classes, multiple interfaces can be extended. Example of using an attribute to determine if the associated SQL make money on amazon mechanical turk for this object should be autogenerated.

Sometimes when you want to get down and dirty with memory you can tell C that you are going to take control and use, gulp, You can get performance benefits from unsafe code, but be careful.

With pointers you can use the standard C symbols: When using pointers be sure to use the "fixed" keyword to make your target memory fixed so the garbage collector doesn't move it around when compacting memory. Defining a web service is very easy. Add a reference to "System. Services" in Visual Studio, add the "using System. Services;" line in your code, subclass from "System. WebService" and finally put the "[WebMethod]" attribute on your method.

Delegates are objects that know how to run a method. Delegates are a refinement of method pointers in C, but with safety built in.

The delegate object work from home jobs nixa mo bound to a method that takes the exact number and type of variables as arguments how much interest do you earn in a roth ira returns the correct type.

When you use the function name without the parentheses, e. C will pick the correct overloaded method based on the signature. Delegates can be declared anonymously by assigning a delegate to a function prefaced with "delegate" this is easier in a later version of. Net when anonymous functions are employee share option scheme (esos). This improves the readability of the code.

All delegates have multicast capability - they can be chained together to call more than one method. They will be invoked in sequence starting with the first one. If you have a return value, only the last method called will return a value. The other return values are lost forever.

If an uncaught exception is thrown, execution returns directly to the calling code and the remaining delegates are not executed. Use "ref" variables to pass information between chained delegates.

Changes to the variable will be passed on to the next delegate.

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The value of "i" below in the delegate is not used, but a reference to "i" leading to odd situations sometimes. The example below is not the correct usage and resharper will warn you that the delegate is using a reference to an out-of-scope variable.

Oddly enough, by default, C does not throw an exception for numerical overflows or underflows. To have C check, you must use the "check" keyword, or configure your project to check all arithmetic. C will automatically upcast a type for you making a subclass a parent classbut you must explicitly do a downcast, since it might fail.

Don't disappoint the compiler 50 cent money make the world go round lyrics making bad casts - trust is often hard to reclaim.

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What's the difference between "ref" and "out"? Covariance and Contravariance allow implicit reference conversions for array types, delegate types, and generic type auguments. These concepts apply to type safety for return values and method parameters. The terms covariance and contravariance are from category theory and describe the order of a set of types forex education sinhala either general options trading mechanics specific, or specific to general using covariant or contravariant functors.

Important for the topic is the Investment options south africa Liskov's Substitiution Principle LSPwhere a more dervived object can stand in for an ancestor object e. The compiler's job is to detect if there is any possibility of type unsafety.

Unless you tell it you take responsibility by using something like a cast, it will not compile - it's to protect you.

The compiler is your friend. But only references can be used for covariance. Covariance and Contravariance were introduced to let generic interfaces and generic types to work as developers would expect. If a return value or parameter is invariant, you must use the exact type as the formal declaration. You cannot substitue a more or less dervived type, i. Covariance is substituting a more derived type to a less derived type.

If the returned type is allowed to be more derived than expected, e. Return values in C are covariant. Generic interfaces can support covariance if they use the "out" modifier. This means the type can only be used in "output positions", not being passed in as arguments, to avoid type safety issues. A delegate may have more specific parameter types than its method target.

This is an example of contravariance. The tertiary operator '? If the value before waitforexit c# '?? If the value is null, the value after the '?? The two fpls stock market below work identically. HtmlEncode to encode strings for display in the browser.

This is useful when you need to know if a particular page has been viewed. Logic for recording the event is done elsewhere and then calls this routine. If you only have a string to transmit between your server and client, you can cheat and use the "Response. StatusDescription" to pass a string message. In the client, invoke a url on the server and look at the "StatusDescription" field for your tiny bit of info. When a respondent is forwarded to this page, they are redirected to another page based on the value of "x" All their GET parameters are passed on as well.

Your command may really taking too long in the database and has been killed. You can increase the default time of 30 seconds by using the "CommandTimeout" field on the "Command" object as shown below:. Don't be misled by the database connection string option, "Connection Timeout", e.

That timeout is for getting the connection, not for how long it queries the database. Example of a utility function that uses ExecuteScalar, and a utility function to free resources which is now obsolete - you should use the "using" construct. Since the default direction is "Input". Performance implications of the shortcut method are not known. For connections, this will close the connection. If you include the 'Application Name' in the connection string, the SQL profiler can show that to you.

This makes db tuning easier. If this method throws an exception, it will pass the test. If it doesn't throw an exception, it will fail the test. By default a random number generator is seeded, in part, with the time. But if you are creating multiple random number generators for parallel execution you need something better to seed Random.

GetFiles will sometimes return more than you want. It will also return files whose extension has extra characters. For example, you may want to find a "config" directory which is a few levels above your executing directory. Use something like "Assmebly. Using a Timer with a TimerCallback you can tell.

Net to repeatedly invoke a method on a schedule. The code is a little verbose for instructional purposes. By default dev studio creates a small file for you called "AssemblyInfo. Inside are various assembly-level attributes.

If you fill these in, then when the. The "decimal" struct gives 28 significant digits and may be used for most currency applications. Use the "m" suffix for constants. If your target machine may not have. Net installed, you can install Dotnetfx. It is found in a directory like "C: For security reasons, only clients on the local host can access the web page version of a web service.

To allow any client to access the service, put the following in the web. This gets rid of the "The test form is only available for requests from the local machine. Enums in C are well developed and have many interesting methods.

Enums derive from System. Enum which contain methods like Format and GetName. GetValues will return all the possible values of an enum. By default int values are assigned starting with zero. It does not perform custom type conversions. Use "sealed" as a method modifier so no subclass can extend the class like java's "final".

You can also seal methods so they cannot be overriden, but they can be hidden. In addition to these Access Modifiers, the '[assembly: InternalsVisibleTo "Friend" ]' allows access to members from other assemblies for testing code. With MSBuild it's a little trickier. This tiny helper function creates the entry and closes it. The "source" argument is the name of your application. VS provides regular expressions in replacing string which can be a lifesaver.

Here's a few examples of operations to be performed on many files:. What the RE means: C provides a way to release resources when an object dies. This produces the following, but not reliably since the Console. Out may have been closed by then. One of the great things about C and Java is automatic garbage collection.

Instead of having to specifically free memory, the Garbage Collector GC runs occassionally and frees the memory of unused objects for us. The GC runs on a separate thread and starts at the root of an application and marks all objects that can be referenced. Afterwards it looks at all the objects and frees, or collects, all the objects without the mark.

After the collection, the GC moves all remaining "live" objects to the start of the heap to avoid memory fracturing. The GC separates objects into three generations: Gen0 contains objects that are freshly created.

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Gen1 are objects who have survived a collection. Gen2 objects are long lived. Since most of the churn happens in the Gen0 objects, these can be collected frequently and Gen1 and Gen2 objects will be collected less frequently. The Large Object Heap LOH is a special heap used for very large objects. The GC uses special rules in handling these objects since they are different than regular objects.

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You can have the GC notify you when it is about to start a collection cycle by hooking into "GC. When disposing of objects, the garbage collector puts objects with finalizers in a special collection that will have their finalizers called by one or more threads.

Be careful accessing a class's static variables like decrementing a counter of objects since the CLR may create more than one finalizer-running thread. After it's finalizer has been called an object will be eligible to be discarded during the next garbage collection round. Sometimes objects may not be important enough to be kept in memory if we are running low on memory.

In this case we can use the "WeakReference" class to point to these objects. The Garbage Collector will not count these references when deciding to reap these objects. Using the CLSCompliant true attribute marks the assembly as being Common Language Specification compliant, so VB and other. Net languages can use your assembly.

When compiling with this attribute, the compiler warns you with the error message CS of non-compliant issues like exposed variable names differing only in case.

If you have lots of test xml files for creating objects and you need to add a new attribute, it's easy with regular expressions. Enter "control-h" to bring up the Replace dialogue box and select the "Use: The final result is.

Looking ahead to Anonymous methods in C 2. We don't have to declare a real method, we can just inline it:. Learning C by Example Toggle navigation. WriteLine "inside static construtor WriteLine "inside regular construtor Test2 inside regular construtor WriteLine "planes top speed: Write "Please enter your favorite animal: WriteLine msg ; Console.

WriteLine "plane's top speed: WriteLine "jet's top speed: IComparable, IFormattable, IConvertible, IComparableIEquatable. Write "Press 'Enter' to exit. UtcNow - startTime; Console. Write "press return to exit.

ParseExact "", "dd-MM-yyyy", System. We have failed the compiler. Write "Converted circle to square! WriteLine "I'm being disposed!

CreateInstance type, paramObject. GetMethod "MyMethod" ; if methodInfo! MyObject myObject; foreach MethodInfo meth in myObject. GenerateSQL" ,false ; if attr! GenerateSQL attr[0]; if gs. Sleep ; Console. EndInvoke result ; Console. Write "End of Program. WriteLine "End of Program. Arithmetic operation resulted in an overflow.

Main String[] args in C: Renamer ref name ; Console. Replace "bin", "". AddDays ; Response. Write "Listening for changes in 'C: Read bBuffer, 0, int length ; fileStream. BinaryWrite bBuffer ; response. AddMonths 6 ; Response. Unable to read data from the transport connection: The connection was closed. ASCII ; return streamReader.

Close ; if httpWebResponse. ExecuteReader ; if reader! WriteLine "problem with sql: Flush ; throw new Exception "executeSQLUpdate: WriteLine "Authors whose state is CA: Char, 2 ; param.

ExecuteReader ; while reader. Add new SqlParameter "name", "OHenry" ; dataAdapter. Fill dataSet, "dataTable1". GetProjectList "Test1", "en-UK", "gender: ToXml ; write "manager. Looking at file "C: AssemblyCompany "Acme Enterprises" ]. RemoveAt i ; arrayList. Start processStartInfo ; process.

Append " said, '". Append ", it was his cousin. Odysseus said, 'Hector, it was his cousin.

Set at compile time. OnBeforeInstall savedState ; this. WriteEntry message, type ; oEV. Replace dirty, "". Replace thisInput, "". WriteLine " bad line: AreEqual " name test", Util. WriteLine "Help, I'm being destroye. Help, I'm being destroye.

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