I have class and there are a lot of properties in it. Is there a functionality of visual studio to reach all the properties easily. I do not want to use a constructor.
This is the class:
Assignment a = new Assignment()
{
}
And this is what I want to do automaticly so i can fill the values:
Assignment a = new Assignment()
{
prop1 = ,
prop2 = ,
prop3 = ,
prop4 = ,
prop5 =
//...
};
If you need to ensure that all properties are filled, I would use a constructor.
If you do not require all properties or prefer to use an object initialiser, then the closest solution would be ReSharper's Control+Space, which brings up each property. As you select them (and assign them) the list gets shorter, so you only select from the remaining unassigned properties. I am not sure if there is a better way.
Related
I have a method that takes multiple properties from an object and I want to safely refactor it to simply take the entire object.
I want to change:
var control = new Control
{
Prop1 = 1,
Prop2 = 2
};
TheMethod(control.Prop1, control.Prop2, "foo");
Into:
var control = new Control
{
Prop1 = 1,
Prop2 = 2
};
TheMethod(control, "foo");
I could not find a ReSharper refactoring that can help. Is there a series of steps I can perform that will safely do this refactoring?
You can use ReSharper's Change Signature refactoring to change the method's signature as you like. You can specify a default value for the newly introduced parameter (of type Control). If that doesn't handle all your cases, you can then use Structural Search and Replace to replace the method's parameters as you see fit.
Replacing the method's parameters of Prop1 and Prop2 to pass the type Control would look like this:
TheMethod(Control control, string value)
{
}
Suppose I have a very large list of objects and each object in the list has the following properties: ID, Name, Make, Model, Color, Price
I know that if I want to quickly locate an object in the list I can use an Indexer and search for the object using it's ID.
But once I locate the object how do I change more than one property at the same time?
I thought about returning the MyClass Object in the get property of the Indexer so that I have access to all of its properties. However, I don't know what to do in the set property of the Indexer to make it work. Below is my code
public MyClass this[int id]
{
get {return myObjectList.FirstOrDefault(item => item.ID == id);}
set {// something = value;}
}
But once I locate the object how do I change more than one properties at the same time?
It looks like you want to do something like
List[4] = {Name = "name",
Make = "make",
Model = "model",
Color = "color",
Price = "price
};
Which is not possible in C#. There's no syntax to set multiple properties of an existing object simultaneously. You can create a new object and replace the one in the list:
List[4] = new MyClass {
Name = "name",
Make = "make",
Model = "model",
Color = "color",
Price = "price
};
But that's creating a new object, not modifying an existing one.
The only way to set multiple properties is with individual sets:
MyClass obj = List[4];
obj.Name = "name";
obj.Make = "make";
obj.Model = "model";
ojb.Color = "color";
obj.Price = "price";
Note that this does not involve the setter of the index property at all. It's not uncommon for collections to have a get-only indexer so that the list itself cannot be mutated through the indexer, although the properties of the objects inside can.
I am retrieving 4 Fields from my database table. Now i want to add them to a dynamic list <>. How to add those into the list.
I tried this :
public class myclass
{
public string StdDetails, StdAdderID;
public DateTime StdAddedDate, StdAddedTime;
}
public void buttonClick()
{
List<myclass> StdList = new List<myclass>();
myclass mc = new myclass();
OdbcCommand readStd =
new OdbcCommand("SELECT StdDetails, StdAddedDate," +
"StdAddedTime, StdAdderID" +
"FROM Students", Conn);
OdbcDataReader readStdreader =
readStd.ExecuteReader(CommandBehavior.SingleRow);
while (readStdreader .Read())
{
mc.StdDetails = readStdreader.GetString(0);
mc.StdDetails = readStdreader.GetString(3);
mc.StdDetails = readStdreader.GetDate(1);
mc.StdDetails = readStdreader.GetDateTime(2);
StdList.Add(mc);
}
MessageBox.Show(StdList[0].ToString());
}
In the message box the value isn't displayed? what to do.please help
//SORRY FOR THE TYPOS :
replace these 3 lines :
mc.StdDetails = readStdreader.GetString(3);
mc.StdDetails = readStdreader.GetDate(1);
mc.StdDetails = readStdreader.GetDateTime(2);
with :
mc.StdAddedDate= readStdreader.GetString(3);
mc.StdAdderID= readStdreader.GetDate(1);
mc.StdAddedTime= readStdreader.GetDateTime(2);
You're only creating a single instance of myclass, so your list will be full of references to the same object. You want this instead:
while (readStdreader.Read())
{
myclass mc = new myclass();
mc.StdDetails = readStdreader.GetString(0);
mc.StdAdderID = readStdreader.GetString(3);
mc.StdAddedDate= readStdreader.GetDate(1);
mc.StdAddedTime = readStdreader.GetDateTime(2);
StdList.Add(mc);
}
Note how I've changed the properties that are assigned, too - the code you posted attempts to assign to StdDetails repeatedly.
You also haven't overridden ToString in myclass, so calling ToString() isn't going to give you anything particularly useful.
Additionally:
You should look into the .NET naming conventions; your naming is all over the shop at the moment. (What does std mean here? You've used it for almost everything...)
Public fields are a really bad idea; use properties instead
Use using statements to close readers, commands, connections etc in a reliable way.
It does not work that way.
First, you have to move MyClass mc = new MyClass(); inside the while, because you must create a new instance every time and not change the existing one.
Second, calling StdList[0].ToString(); will simply output the MyClass name, as you didn't provide an override for the ToString() method.
Third, in your while you're always using the StdDetails property, but I think this is a typo, as it wouldn't compile (you're assigning a String to a DateTime the third and fourth time, and the compiler doesn't like it).
Try with StdList[0].StdDetails instead of StdList[0].ToString() in the message box.
There are two fundamental issues here:
You are reusing the same instance of myclass every time. That means that your list contains the same instance over and over, and since you update that instance every time the loop iterates, its value is that of the last value read from the DB. You need to do a mc = new myclass() inside your while loop.
Your myclass definition doesn't override ToString(). So calling StdList[0].ToString() at the end will just use the default ToString() implementation, which returns the type name, not anything meaningful.
Two things. You are re-assigning values to only the StdDetails property of myclass, and you aren't accessing any particular property in the MessageBox. Need to do:
while (readStdreader .Read())
{
myclass mc = new myclass();
mc.StdDetails = readStdreader .GetString(0);
mc.StdAdderID = readStdreader .GetString(3);
mc.StdAddedDate = readStdreader .GetDate(1);
mc.StdAddedDate = readStdreader .GetDateTime(2);
StdList.Add(mc);
}
MessageBox.Show(StdList[0].StdDetails.ToString());
I saw a few days ago this syntax and wondered if someone could tell me how it is called, how does it work and where is it useful.
When I ask how does it work I mean that the Setters property is readonly(get),
And the second is what do this braces mean: "Setters = {".
http://msdn.microsoft.com/en-us/library/ms601374.aspx
Thanks
datagrid.CellStyle = new Style(typeof(DataGridCell))
{
// Cancel the black border which appears when the user presses on a cell
Setters = { new Setter(Control.BorderThicknessProperty, new Thickness(0)) } // End of Setters
} // End of Style
It is call object initializer and collection initializer and it allows you to set properties in the { .. } block when calling a constructor. Inside the block, you're using Setters = { ... } which is a collection initializer - it allows you to specify elements of a collection (here, you don't have to create a new instance of the collection - it just adds elements in curly braces). For more information see this MSDN page.
In general, the syntax of object initializers has a few options:
// Without explicitly mentioning parameter-less constructor:
new A { Prop1 = ..., Prop2 = ... }
// Specifying constructor arguments:
new A(...) { Prop1 = ..., Prop2 = ... }
The syntax for collection initializers looks like this:
// Creating new instance
new List<int> { 1, 2, 3 }
// Adding to existing instance inside object initializer:
SomeList = { 1, 2, 3 }
It is worth mentioning that this is closely related to anonymous types (where you don't give a type name - the compiler generates some hidden type and you can work with it using var):
// Create anonymous type with some properties
new { Prop1 = ..., Prop2 = ... }
All of these features are new in C# 3.0. See also this SO post which explains some tricky aspect of collection initializers (in the style you're using them).
instantiated the new object Style, and than setting its property Setters It's a c# 3.0 feature.
It seems to be setting default values when the object is being made. This is kind of like passing values to the constructor, but you aren't limited to just the options the constructor gives you.
Is there a way to add a property to the objects of a Linq query result other than the following?
var query = from x in db.Courses
select new
{
x.OldProperty1,
x.OldProperty2,
x.OldProperty3,
NewProperty = true
};
I want to do this without listing out all of the current properties of my object. There are many properties, and I don't want to have to update this code whenever I may change my class.
I am still learning with LINQ and I appreciate your suggestions.
Add it with partial classes:
public partial class Courses
{
public String NewProperty { get; set; }
}
Then you can assign it after you've created the object.
I suppose you could return a new object composed of the new property and the selected object, like this:
var query = from x in db.Courses
select new
{
Course = x,
NewProperty = true
};
eking's answer will be the most straightforward approach.
If that doesn't work for you (because you need to pass the results around or whatever), and assuming the class you're dealing with already defines the property you want to set, you could create a copy constructor or factory method that takes an existing instance plus the value of the property you want to set:
var query = from x in db.Courses
select new Course(x, valueOfNewProperty);
Alternatively, if Course doesn't define the property, you could subclass it and use the same approach:
var query = from x in db.Courses
select new CourseWithExtraProperty(x, valueOfNewProperty);
(obviously, pick a better name for your subclass)
Again, though, unless you really need to do this, stick with eking's solution.
ServiceStack has a built-in way to handle this with the PopulateWith method.
Here's a code example.
foreach (var item in results)
{
var test1 = new ItemDto().PopulateWith(item);
test1.extraField1 = "extra";
response.Add(test1);
}`
And if you're not using ServiceStack, you can always use AutoMapper.
CreateMap<Foo, Bar>().ForMember(x => x.ExtraBarProperty, opt => opt.Ignore());
If you are looking to dynamically add a property to an object this could be a solution.
This is what has worked for me, I also had a concern and it was what happened with those domain objects that had many properties, the maintainability for any changes in the object was absurd, I managed to build an implementation with LINQ - ExpandObject - Reflection, which helped to keep my object dynamic and only add the additional properties that my view logic required.
var expandedModel = db.Courses.Select(x =>
{
dynamic expandObject = new ExpandoObject();
expandObject.NewProperty= $"PropertyValue";
foreach (var property in x.GetType().GetProperties())
{
((IDictionary<string, object>)expandObject).Add(property.Name, property.GetValue(x));
}
return expandObject;
}).ToList();