I am trying to call a static function from a class but the intellisense is not picking it up?
the function return
public static ArrayList GetInfo(int infoID)
and i am calling from somewhere else in another class, I was trying to do something like
var myitem = myClassName.GetInfo(x);
but intelisense doesnt pick it up... as I type myClassName.
How can i call it? if at all possible
PS: I cant change the signature of the method :(.
normally you do have a namespace as well, plus that static method has to be inside it's own class, for example, something like:
namespace MyHelpers {
public static class ArrayHelpers {
public static ArrayList GetInfo(int infoID) { ... }
}
}
now, no matter where you are in your application, and if that library is referenced to your current project you simply call it
ArrayList myitem = MyHelpers.ArrayHelpers.GetInfo(x);
remember that you need to give the full path and if your namespace is called namespace Model.Helpers { ...
then the full path will be:
ArrayList myitem = Model.Helpers.ArrayHelpers.GetInfo(x);
is you are using the using declaration
using Model.Helpers;
you can use
ArrayList myitem = ArrayHelpers.GetInfo(x);
Static functions cant be accessed with variable name, but with class name. So basicly just call either just GetInfo(int) ( if you want to call it within the class where the GetInfo() is ) or YourClass.GetInfo(int) ( outside the class where GetInfo() is ).
If you are calling outside the class, make sure that you are using same namespace in both, or you are using appropriate using statements.
Did you create the class in a subfolder of your project? If so, you need to call it like this:
subfolder.myclassname.getinfo()
Related
I am getting into C# and I am having this issue:
namespace MyDataLayer
{
namespace Section1
{
public class MyClass
{
public class MyItem
{
public static string Property1{ get; set; }
}
public static MyItem GetItem()
{
MyItem theItem = new MyItem();
theItem.Property1 = "MyValue";
return theItem;
}
}
}
}
I have this code on a UserControl:
using MyDataLayer.Section1;
public class MyClass
{
protected void MyMethod
{
MyClass.MyItem oItem = new MyClass.MyItem();
oItem = MyClass.GetItem();
someLiteral.Text = oItem.Property1;
}
}
Everything works fine, except when I go to access Property1. The intellisense only gives me "Equals, GetHashCode, GetType, and ToString" as options. When I mouse over the oItem.Property1, Visual Studio gives me this explanation:
MemberMyDataLayer.Section1.MyClass.MyItem.Property1.getcannot be accessed with an instance reference, qualify it with a type name instead
I am unsure of what this means, I did some googling but wasn't able to figure it out.
In C#, unlike VB.NET and Java, you can't access static members with instance syntax. You should do:
MyClass.MyItem.Property1
to refer to that property or remove the static modifier from Property1 (which is what you probably want to do). For a conceptual idea about what static is, see my other answer.
You can only access static members using the name of the type.
Therefore, you need to either write,
MyClass.MyItem.Property1
Or (this is probably what you need to do) make Property1 an instance property by removing the static keyword from its definition.
Static properties are shared between all instances of their class, so that they only have one value. The way it's defined now, there is no point in making any instances of your MyItem class.
I had the same issue - although a few years later, some may find a few pointers helpful:
Do not use ‘static’ gratuitously!
Understand what ‘static’ implies in terms of both run-time and compile time semantics (behavior) and syntax.
A static entity will be automatically constructed some time before
its first use.
A static entity has one storage location allocated, and that is
shared by all who access that entity.
A static entity can only be accessed through its type name, not
through an instance of that type.
A static method does not have an implicit ‘this’ argument, as does an
instance method. (And therefore a static method has less execution
overhead – one reason to use them.)
Think about thread safety when using static entities.
Some details on static in MSDN:
Static Classes in C#
Static Constructors in C#
This causes the error:
MyClass aCoolObj = new MyClass();
aCoolObj.MyCoolStaticMethod();
This is the fix:
MyClass.MyCoolStaticMethod();
Explanation:
You can't call a static method from an instance of an object. The whole point of static methods is to not be tied to instances of objects, but instead to persist through all instances of that object, and/or to be used without any instances of the object.
No need to use static in this case as thoroughly explained. You might as well initialise your property without GetItem() method, example of both below:
namespace MyNamespace
{
using System;
public class MyType
{
public string MyProperty { get; set; } = new string();
public static string MyStatic { get; set; } = "I'm static";
}
}
Consuming:
using MyType;
public class Somewhere
{
public void Consuming(){
// through instance of your type
var myObject = new MyType();
var alpha = myObject.MyProperty;
// through your type
var beta = MyType.MyStatic;
}
}
cannot be accessed with an instance reference
It means you're calling a STATIC method and passing it an instance. The easiest solution is to remove Static, eg:
public static void ExportToExcel(IEnumerable data, string sheetName)
{
Remove the static in the function you are trying to call. This fixed the problem for me.
I got here googling for C# compiler error CS0176, through (duplicate) question Static member instance reference issue.
In my case, the error happened because I had a static method and an extension method with the same name. For that, see Static method and extension method with same name.
[May be this should have been a comment. Sorry that I don't have enough reputation yet.]
I know this is an old thread, but I just spent 3 hours trying to figure out what my issue was. I ordinarily know what this error means, but you can run into this in a more subtle way as well. My issue was my client class (the one calling a static method from an instance class) had a property of a different type but named the same as the static method. The error reported by the compiler was the same as reported here, but the issue was basically name collision.
For anyone else getting this error and none of the above helps, try fully qualifying your instance class with the namespace name. ..() so the compiler can see the exact name you mean.
Check whether your code contains a namespace which the right most part matches your static class name.
Given the a static Bar class, defined on namespace Foo, implementing a method Jump or a property, chances are you are receiving compiler error because there is also another namespace ending on Bar. Yep, fishi stuff ;-)
If that's so, it means your using a Using Bar; and a Bar.Jump() call, therefore one of the following solutions should fit your needs:
Fully qualify static class name with according namepace, which result on Foo.Bar.Jump() declaration. You will also need to remove Using Bar; statement
Rename namespace Bar by a diffente name.
In my case, the foollowing compiler error occurred on a EF (Entity Framework) repository project on an Database.SetInitializer() call:
Member 'Database.SetInitializer<MyDatabaseContext>(IDatabaseInitializer<MyDatabaseContext>)' cannot be accessed with an instance reference; qualify it with a type name instead MyProject.ORM
This error arouse when I added a MyProject.ORM.Database namespace, which sufix (Database), as you might noticed, matches Database.SetInitializer class name.
In this, since I have no control on EF's Database static class and I would also like to preserve my custom namespace, I decided fully qualify EF's Database static class with its namepace System.Data.Entity, which resulted on using the following command, which compilation succeed:
System.Data.Entity.Database.SetInitializer<MyDatabaseContext>(MyMigrationStrategy)
Hope it helps
YourClassName.YourStaticFieldName
For your static field would look like:
public class StaticExample
{
public static double Pi = 3.14;
}
From another class, you can access the staic field as follows:
class Program
{
static void Main(string[] args)
{
double radius = 6;
double areaOfCircle = 0;
areaOfCircle = StaticExample.Pi * radius * radius;
Console.WriteLine("Area = "+areaOfCircle);
Console.ReadKey();
}
}
Is there an option to automatically pass this as parameter to a function? For example, you can use [CallerMemberName] to automatically pass string name. I'm looking for exact option with this.
Example:
void PassMeThis([AutomaticThisParam] object source);
and usage:
public class SomeClass{
void SomeMethod(){
PassMeThis(); // instead of PassMeThis(this)
}
}
Yes absolutely. This is called an extension Method.
Create a static class
Public static class MethodExtensions
Add a static method to it like this
public static PassMeThis(this SomeClass model) { // }
Call the method like this (referring to your code example):
this.PassMeThis()
And it's automaticly filled.
I hope thats what you were looking for
If PassMeThis is in the same class (or ancestor), as in your example, there is no point, this is avaiable there, too.
If it is in another class, there is no way to automatically get a reference to the calling object: IS there any way to get a reference to the calling object in c#?
I am a newbie to asp.net and c#..I've been asked to analyse the code of a portal. Please look at the following code and suggest me a way to call the FromDatabase method. I've gone through all the files in the solution but there is no call statement to it.
Here Account and Utility are classes.
public static Account FromDatabase(DbDataRecord dr)
{
return new Account(
Utility.StringFromNull(dr.GetValue(0)),
Utility.StringFromNull(dr.GetValue(1)),
Utility.IntFromNull(dr.GetValue(2)),
Utility.StringFromNull(dr.GetValue(3)),
Utility.StringFromNull(dr.GetValue(4)),
Utility.StringFromNull(dr.GetValue(5)),
Utility.DateTimeFromNull(dr.GetValue(6))
);
}
In what other way can I return the values instead of return new Account().
Thanks in advance!
To use a static method you just use the class, and not an instance of it. I.E.: say your method is in class MyClass, then you just do
MyClass.FromDataBase(yourDataRow);
You can call a static method by using the class name that the static method belongs to...
Example:
public class MyClass {
public static object MyMethod() {}
}
To call it:
MyClass.MyMethod();
Account myAccount = Account.FromDatabase(dr);
call it this way:
NameOfStaticClass.FromDatabase(dbRec)
and NameOfStaticClass is the name of class in witch FromDatabase method is declared
You can call the Account.FromDatabase method by using the typeName of the class it lives in (I assumy it is a method on the Account class itself. However it will always result a Account object.
You can create another method that will parse the DbDataRecord object and return it in any collection object, for example an array.
I am getting into C# and I am having this issue:
namespace MyDataLayer
{
namespace Section1
{
public class MyClass
{
public class MyItem
{
public static string Property1{ get; set; }
}
public static MyItem GetItem()
{
MyItem theItem = new MyItem();
theItem.Property1 = "MyValue";
return theItem;
}
}
}
}
I have this code on a UserControl:
using MyDataLayer.Section1;
public class MyClass
{
protected void MyMethod
{
MyClass.MyItem oItem = new MyClass.MyItem();
oItem = MyClass.GetItem();
someLiteral.Text = oItem.Property1;
}
}
Everything works fine, except when I go to access Property1. The intellisense only gives me "Equals, GetHashCode, GetType, and ToString" as options. When I mouse over the oItem.Property1, Visual Studio gives me this explanation:
MemberMyDataLayer.Section1.MyClass.MyItem.Property1.getcannot be accessed with an instance reference, qualify it with a type name instead
I am unsure of what this means, I did some googling but wasn't able to figure it out.
In C#, unlike VB.NET and Java, you can't access static members with instance syntax. You should do:
MyClass.MyItem.Property1
to refer to that property or remove the static modifier from Property1 (which is what you probably want to do). For a conceptual idea about what static is, see my other answer.
You can only access static members using the name of the type.
Therefore, you need to either write,
MyClass.MyItem.Property1
Or (this is probably what you need to do) make Property1 an instance property by removing the static keyword from its definition.
Static properties are shared between all instances of their class, so that they only have one value. The way it's defined now, there is no point in making any instances of your MyItem class.
I had the same issue - although a few years later, some may find a few pointers helpful:
Do not use ‘static’ gratuitously!
Understand what ‘static’ implies in terms of both run-time and compile time semantics (behavior) and syntax.
A static entity will be automatically constructed some time before
its first use.
A static entity has one storage location allocated, and that is
shared by all who access that entity.
A static entity can only be accessed through its type name, not
through an instance of that type.
A static method does not have an implicit ‘this’ argument, as does an
instance method. (And therefore a static method has less execution
overhead – one reason to use them.)
Think about thread safety when using static entities.
Some details on static in MSDN:
Static Classes in C#
Static Constructors in C#
This causes the error:
MyClass aCoolObj = new MyClass();
aCoolObj.MyCoolStaticMethod();
This is the fix:
MyClass.MyCoolStaticMethod();
Explanation:
You can't call a static method from an instance of an object. The whole point of static methods is to not be tied to instances of objects, but instead to persist through all instances of that object, and/or to be used without any instances of the object.
No need to use static in this case as thoroughly explained. You might as well initialise your property without GetItem() method, example of both below:
namespace MyNamespace
{
using System;
public class MyType
{
public string MyProperty { get; set; } = new string();
public static string MyStatic { get; set; } = "I'm static";
}
}
Consuming:
using MyType;
public class Somewhere
{
public void Consuming(){
// through instance of your type
var myObject = new MyType();
var alpha = myObject.MyProperty;
// through your type
var beta = MyType.MyStatic;
}
}
cannot be accessed with an instance reference
It means you're calling a STATIC method and passing it an instance. The easiest solution is to remove Static, eg:
public static void ExportToExcel(IEnumerable data, string sheetName)
{
Remove the static in the function you are trying to call. This fixed the problem for me.
I got here googling for C# compiler error CS0176, through (duplicate) question Static member instance reference issue.
In my case, the error happened because I had a static method and an extension method with the same name. For that, see Static method and extension method with same name.
[May be this should have been a comment. Sorry that I don't have enough reputation yet.]
I know this is an old thread, but I just spent 3 hours trying to figure out what my issue was. I ordinarily know what this error means, but you can run into this in a more subtle way as well. My issue was my client class (the one calling a static method from an instance class) had a property of a different type but named the same as the static method. The error reported by the compiler was the same as reported here, but the issue was basically name collision.
For anyone else getting this error and none of the above helps, try fully qualifying your instance class with the namespace name. ..() so the compiler can see the exact name you mean.
Check whether your code contains a namespace which the right most part matches your static class name.
Given the a static Bar class, defined on namespace Foo, implementing a method Jump or a property, chances are you are receiving compiler error because there is also another namespace ending on Bar. Yep, fishi stuff ;-)
If that's so, it means your using a Using Bar; and a Bar.Jump() call, therefore one of the following solutions should fit your needs:
Fully qualify static class name with according namepace, which result on Foo.Bar.Jump() declaration. You will also need to remove Using Bar; statement
Rename namespace Bar by a diffente name.
In my case, the foollowing compiler error occurred on a EF (Entity Framework) repository project on an Database.SetInitializer() call:
Member 'Database.SetInitializer<MyDatabaseContext>(IDatabaseInitializer<MyDatabaseContext>)' cannot be accessed with an instance reference; qualify it with a type name instead MyProject.ORM
This error arouse when I added a MyProject.ORM.Database namespace, which sufix (Database), as you might noticed, matches Database.SetInitializer class name.
In this, since I have no control on EF's Database static class and I would also like to preserve my custom namespace, I decided fully qualify EF's Database static class with its namepace System.Data.Entity, which resulted on using the following command, which compilation succeed:
System.Data.Entity.Database.SetInitializer<MyDatabaseContext>(MyMigrationStrategy)
Hope it helps
YourClassName.YourStaticFieldName
For your static field would look like:
public class StaticExample
{
public static double Pi = 3.14;
}
From another class, you can access the staic field as follows:
class Program
{
static void Main(string[] args)
{
double radius = 6;
double areaOfCircle = 0;
areaOfCircle = StaticExample.Pi * radius * radius;
Console.WriteLine("Area = "+areaOfCircle);
Console.ReadKey();
}
}
I'm trying to create a function in C# which will allow me to, when called, return a reference to a given class type. The only types of functions like this that I have seen are in UnrealScript and even then the functionality is hard coded into its compiler. I'm wondering if I can do this in C#. Here's what I mean (code snippet from UnrealScript source):
native(278) final function actor Spawn
(
class<actor> SpawnClass,
optional actor SpawnOwner,
optional name SpawnTag,
optional vector SpawnLocation,
optional rotator SpawnRotation
);
Now in UScript you would call it like this...
local ActorChild myChildRef; //Ref to ActorChild which Extends 'actor'
myChildRef = Spawn(class'ActorChild' ...); //rest of parameters taken out
myChildRef.ChildMethod(); //method call to method existing inside class 'ActorChild'
Which will return a reference to an object of class 'ActorChild' and set it to variable 'myChildRef.' I need to do something similar within C#.
I've looked into Generics but it seems that to use them, I need create an instace of the class where my function lies and pass the 'generic' parameter to it. This isn't very desirable however as I won't need to use the 'Spawn' function for certain classes but I would still need to add the generic parameter to the class whenever I use it.
I guess a simplified question would be, how can I return a type that I do not know at compile time and when the different classes could be far too many to trap.
Pseudo-Code (sticking to UScript class names, i.e. Actor):
//Function Sig
public class<Actor> Create(class<Actor> CreatedClass)
{
return new CreatedClass;
}
//Function call
ActorChild myChild = Create(class'ActorChild');
Any ideas?
EDIT: I would like to avoid explicit typecasts that would occur from the class calling Created. If I can typecast to the desired object within the Created method and return the 'unknown type' whatever that may be, I would be extremely happy.
EDIT 2: Thanks for your answers.
Rather than use a generic class, use a generic method:
public T Spawn<T>() where T : new()
{
return new T();
}
Having said that, I assume you want to do more than just blindly create an instance, otherwise you could just call new MyClass() yourself.
You can use the class System.Type to represent classes. To get references to type objects, you either use typeof (in a scope where the class is actually defined)
System.Type t = typeof(ActorChild);
or the Type.GetType function (if you only know the name of the type)
System.Type t = Type.GetType("NamespaceFoo.ActorChild");
You can then use the reflection API to create an instance
public object Create(System.Type ClassToCreate)
{
return ClassToCreate.GetConstructor(Type.EmptyTypes).Invoke(null);
}
What you're trying to accomplish can be done quite easily with Reflection and something called Dynamic Method Invocation.
Basically, you'll be using the Type object, the Activator.CreateInstance Method and some other nice classes like MethodInfo and ParameterInfo.
Here's an example to get you started:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Reflection;
namespace Reflection
{
class SomeClass
{
private string StringPrimer = "The parameter text is: ";
public SomeClass(string text)
{
Console.WriteLine(StringPrimer + text);
}
public string getPrimer() //supplies the Primer in upper case, just for kicks
{
return StringPrimer.ToUpper();
}
}
class Program
{
static void Main(string[] args)
{
SomeClass s = new SomeClass("this is an example of the classes normal hard-coded function.\nNow try feeding in some text");
string t = Console.ReadLine();
Console.WriteLine("Now feed in the class name (SomeClass in this case)");
Type myType = Type.GetType("Reflection."+Console.ReadLine()); //Stores info about the class.
object myClass = Activator.CreateInstance(myType, new object[] { t }); //This dynamically calls SomeClass and sends in the text you enter as a parameter
//Now lets get the string primer, using the getPrimer function, dynamically
string primer = (string)myType.InvokeMember("getPrimer",
BindingFlags.InvokeMethod | BindingFlags.Default,
null,
myClass,
null); //This method takes the name of the method, some Binding flags,
//a binder object that I left null,
//the object that the method will be called from (would have been null if the method was static)
//and an object array of parameters, just like in the CreateInstance method.
Console.WriteLine(primer);
}
}
}