Develop Reference

Is it possible to easily get variable names in a method as well as their values

Following my Is it possible to have a Function that takes any number of variables of any type?
I have the function that gets any number of any type of variables and it works perfectly
public string funcVars(params object[] paths)
{
string strVars = String.Join(", ", paths.Select(x => x.ToString()));
return strVars;
}
To call it I'd simply need to
string someString ="asd"; int someInt = 123; bool someBool=false;
funcVars(someString,someInt,someBool);
And the output would be
asd,123,false
is there any simple way I can also get the variable names as well as their values, so the output would be
asd,123,false,someString,someInt,someBool //(or any other similar form)
Or do I need to hardcode the names every time I call my method ?
funcVars("someString","someInt","someBool",someString,someInt,someBool);

What you really should be doing is creating a class to hold your variables:
internal class MyValues
{
internal string SomeString { get; set; }
internal int SomeInt { get; set; }
internal bool SomeBool { get; set; }
}
Then you can pass an instance of your class:
var mv = new MyValues() { SomeString = "asd", SomeInt = 123, SomeBool = false };
funcVars(mv);
Here is funcVars:
public string funcVars(MyValues values)
{
string strVars =
String.Join(", ", new[] { values.SomeString,
values.SomeInt.ToString(), values.SomeBool.ToString() });
return strVars;
}

Straight up stealing roy.ap's code and adding the "nameof()" method since getting the name of the property seemed to be apart of the question.
class Program
{
internal class MyValues
{
internal string SomeString { get; set; }
internal int SomeInt { get; set; }
internal bool SomeBool { get; set; }
}
static void Main(string[] args)
{
var mv = new MyValues() { SomeString = "asd", SomeInt = 123, SomeBool = false };
Console.WriteLine(funcVars(mv));
Console.ReadLine();
}
public static string funcVars(MyValues values)
{
string strVars =
String.Join(", ", new[]
{
nameof(values.SomeString), values.SomeString,
nameof(values.SomeInt), values.SomeInt.ToString(),
nameof(values.SomeBool), values.SomeBool.ToString()
});
return strVars;
}
}
There really isn't a way to get the variable names via the the function itself because the scope changes once you're in the method. That is even if you pass an array of objects, if you perform a foreach to go through each object you will give the individual objects a new scope specific name.

No, because the variables are not actually passed
No it is not possible, because the variables themselves are not actually passed. Their values are passed.
Consider this code:
string someString ="asd"; int someInt = 123; bool someBool=false;
funcVars(someString,someInt,someBool);
In your call to funcVars, all the parameters are passed by value. All three variables are copied, and copy of them is put on the stack. These stack variables are identified by completely different symbols-- (e.g. paths[0],paths[1], etc.)
After all, what would happen if you called it like this?
funcVars("Hello",245+25,test != null);
Obviously those values do not have variable names. There is no way your function can possibly retrieve what doesn't exist.
Use ExpandoObject instead
The System.Dynamic.ExpandoObject seems like a really good fit for this problem.
var args = new System.Dynamic.ExpandoObject();
args.SomeString = "hello";
args.SomeInt = 32;
args.SomeBool = false;
funcVars(args);
public static string funcVars(ExpandoObject inputs)
{
var sb = new StringBuilder();
foreach (KeyValuePair<string, object> kvp in inputs)
{
sb.Append(String.Format("{0} = {1}", kvp.Key, kvp.Value);
}
return sb.ToString();
}

Assign reference to list properly c#

I'm trying to add strings to a List<string> so I can print them with a loop in a certain point of time, being more specific here is part of my code:
public class Foo{
public string propertyA;
public string propertyB;
public string propertyC;
public List<string> list;
Public Foo(){
list = new List<string>();
list.Add(propertyA);
list.Add(propertyB);
list.Add(propertyC);
}
}
In later code, after assigning propertyA and the other variables and trying to iterate over the List I get empty strings. I require the properties to be in the list. My questions is which would be the best way to achieve this?

Looks like you are getting empty strings because when you are adding to the list the values in your properties have not been set at the time that the Foo() constructor is called...
Try passing values and setting them in the Foo constructor as follows:
public class Foo{
public string propertyA;
public string propertyB;
public string propertyC;
public List<string> list;
Public Foo(string propA, string propB, string propC){
propertyA = propA;
propertyB = propB;
propertyC = propC;
list = new List<string>();
list.Add(propertyA);
list.Add(propertyB);
list.Add(propertyC);
}
}
Alternatively you could add the values to the list at a later time when the properties are actually set and not in the constructor e.g.
public string PropertyA
{
//set the person name
set { propertyA = value;
list.Add(value);
}
//get the person name
get { return propertyA; }
}
...

What you're seeing is expected behavior. Updating "propertyA", etc later on won't update the strings that have already been added to the collection.
You could consider using a Dictionary instead of your own class, and then adding and updating elements is easier: (and you don't have to keep updating your class with new property names)
var properties = new Dictionary<string, string>();
properties.Add("propertyA", "some value of property A");
properties["propertyA"] = "some new value";
And when you want to display the values later:
MessageBox.Show(string.Join(Environment.NewLine, properties));
Alternatively, if you want a class and the option of adding properties to it, then maybe extending the Dictionary class like this will at least make things easier to maintain, so you can add more properties that'll stay in sync with the underlying Dictionary, with a minimum of fuss.
public class PropertyCollection : Dictionary<string, string>
{
public string PropertyA
{
get { return GetValue(); }
set { StoreValue(value); }
}
public string PropertyB
{
get { return GetValue(); }
set { StoreValue(value); }
}
protected string GetValue([CallerMemberName] string propName = "")
{
if (ContainsKey(propName))
return this[propName];
return "";
}
protected void StoreValue(string propValue, [CallerMemberName] string propName = "")
{
if (ContainsKey(propName))
this[propName] = propValue;
else
Add(propName, propValue);
}
}

If you want to assign propertyA, B, C after an instance of Foo is created and enumerate them, you could try something like this:
public class Foo
{
public string propertyA { get { return list[0]; } set { list[0] = value; } }
public string propertyB { get { return list[1]; } set { list[1] = value; } }
public string propertyC { get { return list[2]; } set { list[2] = value; } }
public List<string> list = new List<string>() {"", "", ""};
}
For the reasons why the code behaves in a way you might not expect, see How are strings passed in .NET?

C# Object Initializer : Set Property from another one

I have the following object where in my constructor I add a new Guid as the Id.
public class MyObject
{
public MyObject()
{
Id = Guid.NewGuid().ToString();
}
public String Id { get; set; }
public String Test { get; set; }
}
I want to do something like that in an object initializer :
var obj = new MyObject
{
Test = Id; // Get new GUID created in constructor
}
Is it possible?

No, you can't do that. You'd have to just set it in a separate statement:
var obj = new MyObject();
obj.Test = obj.Id;
The right-hand side of the property in an object initializer is just a normal expression, with no inherent connection to the object being initialized.
If this is something you regularly want to do with one specific type, you could add a method:
public MyObject CopyIdToTest()
{
this.Test = Id;
return this;
}
and then use:
MyObject obj = new MyObject().CopyIdToTest();
or with other properties:
MyObject obj = new MyObject
{
// Set other properties here
}.CopyIdToTest();

No -- you can't access an object's properties inside an initializer. The initializer is basically some syntactic sugar for programmers.
Consider situations like:
class Program
{
static void Main()
{
var Id = "hello";
var obj = new MyObject
{
Test = Id // Get new GUID created in constructor
};
}
}
The Id you'd assign (if your idea was valid, which again, it isn't) isn't necessarily the Id you'd be getting.

Using DefaultIfEmpty with an object?

I saw an example on MSDN where it would let you specify the default value if nothing is returned. See below:
List<int> months = new List<int> { };
int firstMonth2 = months.DefaultIfEmpty(1).First();
Is it possible to use this functionality with an object? Example:
class object
{
int id;
string name;
}
code:
List<myObjec> objs = new List<myObjec> {};
string defaultName = objs.DefaultIfEmpty(/*something to define object in here*/).name;
UPDATE:
I was thinking I could do something like this:
List<myObjec> objs = new List<myObjec> {};
string defaultName = objs.DefaultIfEmpty(new myObjec(-1,"test")).name;
But haven't been able to. It should be noted that I am actually trying to use this method on an object defined in my DBML using LINQ-To-SQL. Not sure if that makes a difference in this case or not.

You need to pass an instantiated class as a parameter of the DefaultIfEmpty.
class Program
{
static void Main(string[] args)
{
var lTest = new List<Test>();
var s = lTest.DefaultIfEmpty(new Test() { i = 1, name = "testing" }).First().name;
Console.WriteLine(s);
Console.ReadLine();
}
}
public class Test
{
public int i { get; set; }
public string name { get; set; }
}
To add to it and make it a bit more elegant (IMO) add a default constructor:
class Program
{
static void Main(string[] args)
{
var lTest = new List<Test>();
var s = lTest.DefaultIfEmpty(new Test()).First().name;
Console.WriteLine(s);
Console.ReadLine();
}
}
public class Test
{
public int i { get; set; }
public string name { get; set; }
public Test() { i = 2; name = "testing2"; }
}

As per the MSDN page on this Extension Method you can do what you want:
http://msdn.microsoft.com/en-us/library/bb355419.aspx
Check the sample on this page for an example on how to use this with an object.

i must admit i am not too sure i understand your question, but i'll try to suggest using double question mark if the returned object might be null. Like so:
myList.FirstOrDefault() ?? new myObject();

You can create a default Object Like this:
Object o_Obj_Default = new Object();
o_Obj_Default.id = 3;
o_Obj_Default.name = "C";
And add it to your default value :
string defaultName = objs.DefaultIfEmpty(o_Obj_Default).First().name;
If your list "objs" is empty, the result will be "C"

Is it possible to modify the attribute of a property at runtime?

Is it possible to modify the attribute of a property at runtime?
let's say I have some class:
public class TheClass
{
[TheAttribute]
public int TheProperty { get; set; }
}
Is there a way to do this?
if (someCondition)
{
// disable attribute. Is this possible and how can this be done?
}

No this is not possible. You cannot modify attribute values from metadata, or metadata in general, at runtime
Strictly speaking the above is not true. There are certain APIs which do allow allow for some metadata generation and modification. But they are very scenario specific, (ENC, profiling, debugging) and should not be used in general purpose programs.

It depends; from a reflection perspective: no. You can't. But if you are talking about attributes used by System.ComponentModel in things like data-binding, they you can use TypeDescriptor.AddAttributes to append extra attributes. Or other customer models involving custom descriptors. So it depends on the use-case.
In the case of xml serialization, it gets more interesting. Firstly, we can use fun object models:
using System;
using System.Xml.Serialization;
public class MyData
{
[XmlAttribute]
public int Id { get; set; }
[XmlAttribute]
public string Name { get; set; }
[XmlIgnore]
public bool NameSpecified { get; set; }
static void Main()
{
var ser = new XmlSerializer(typeof(MyData));
var obj1 = new MyData { Id = 1, Name = "Fred", NameSpecified = true };
ser.Serialize(Console.Out, obj1);
Console.WriteLine();
Console.WriteLine();
var obj2 = new MyData { Id = 2, Name = "Fred", NameSpecified = false };
ser.Serialize(Console.Out, obj2);
}
}
The bool {name}Specified {get;set;} pattern (along with bool ShouldSerialize{name}()) is recognised and used to control which elements to include.
Another alternative is to use the non-default ctor:
using System;
using System.Xml.Serialization;
public class MyData
{
[XmlAttribute]
public int Id { get; set; }
public string Name { get; set; }
static void Main()
{
var obj = new MyData { Id = 1, Name = "Fred" };
XmlAttributeOverrides config1 = new XmlAttributeOverrides();
config1.Add(typeof(MyData),"Name",
new XmlAttributes { XmlIgnore = true});
var ser1 = new XmlSerializer(typeof(MyData),config1);
ser1.Serialize(Console.Out, obj);
Console.WriteLine();
Console.WriteLine();
XmlAttributeOverrides config2 = new XmlAttributeOverrides();
config2.Add(typeof(MyData), "Name",
new XmlAttributes { XmlIgnore = false });
var ser2 = new XmlSerializer(typeof(MyData), config2);
ser2.Serialize(Console.Out, obj);
}
}
Note though that if you use this second approach you need to cache the serializer instance, as it emits an assembly every time you do this. I find the first approach simpler...

Attributes are baked into code at compilation time. The only way you can define new attributes at run time is to generate new code at runtime (using Reflection.Emit, for example). But you cannot change the attributes of existing code.

You can put Boolean variable in the class to disable/enable the property instead of disabling it at run time.

You might want to look at this http://social.msdn.microsoft.com/Forums/en-US/csharpgeneral/thread/5b0d356d-d006-43ff-bfcd-aa90dd8de6db
And Dave Morton's explanation on this blog http://blog.codinglight.com/2008/10/changing-attribute-parameters-at.html

Sounds like you want to consider implementing IXmlSerializable

You can implement IDataErrorInfo, then check range in Validate method.
public string this[string property] {
get { return Validate(property); }
}
public string Error { get; }
protected virtual string Validate(string property) {
var propertyInfo = this.GetType().GetProperty(property);
var results = new List<ValidationResult>();
var result = Validator.TryValidateProperty(
propertyInfo.GetValue(this, null),
new ValidationContext(this, null, null) {
MemberName = property
},
results);
if (!result) {
var validationResult = results.First();
return validationResult.ErrorMessage;
}
return string.Empty;
}
In sub class
protected override string Validate(string property) {
Debug.WriteLine(property);
if (property == nameof(YourProperty)) {
if (_property > 5) {
return "_property out of range";
}
}
return base.Validate(property);
}