Develop Reference

Using reflection to iterate a class properties that has nested classes

I found this answer here at SO, Get nested property values through reflection C#, though when I run it in my case, it also tries to dump/recurse on e.g. a string's property, like Name, and when, it throws an exception.
My classes look like this
public class MyModels
{
public int Id { get; set; }
public DateTime EditDate { get; set; }
public string EditBy { get; set; }
}
public class Person
{
public string Name { get; set; }
}
public class Organization
{
public Person Person { get; set; }
public Organization()
{
Person = new Person();
}
public string Name { get; set; }
}
public class Company : MyModels
{
public Organization Organization { get; set; }
public Company()
{
Organization = new Organization();
}
public string Description { get; set; }
}
And here's the code from the linked answer
var objtree = "";
void DumpObjectTree(object propValue, int level = 0)
{
if (propValue == null)
return;
var childProps = propValue.GetType().GetProperties();
foreach (var prop in childProps)
{
var name = prop.Name;
var value = prop.GetValue(propValue, null);
// add some left padding to make it look like a tree
objtree += ("".PadLeft(level * 4, ' ') + $"{name} = {value}") + Environment.NewLine;
// call again for the child property
DumpObjectTree(value, level + 1);
}
}
DumpObjectTree(itemData);
What I want is to iterate all the properties and check their value.
When I run the above code sample:
it first finds Organization, and recurse
at 1st level it finds Person, and recurse
at 2nd level if finds Name, and recurse
at 3rd level it throws an exception when it tries to GetValue for Name
If I remove my nested classes, and run it:
it first finds Description, and recurse
at 1st level it throws an exception when it tries to GetValue for Description
How do I make it to not try to dump/recurse on properties of type string, datetime, etc., like e.g. Name, Description?
The exception message says: "Parameter count mismatch."
As a note , the expected output/content in the objtree variable is e.g.
Organization = MyNameSpace.Models.Organization
Person = MyNameSpace.Models.Person
Name = TestName
Name = TestCompany
Description = Some info about the company...
Id = 1
EditDate = 31/08/2019
EditBy = user#domain.com

The reason for the exception is that string has a property named Chars. You normally don't see this property, because it's the indexer used when you do something like char c = myString[0];.
This property obviously needs a paramter (the index), and since you don't provide one, an exception is thrown.
To filter the types you don't want to recurse you need to extend the first line in the method. For example
if (propValue == null) return;
if (propValue.GetType().Assembly != Assembly.GetExecutingAssembly())
return;
This will only recurse through types declared in your assembly. If you want special filtering you need to adjust it.
Your current specification ("of type string, datetime etc") is not specific enough to give an exact solution, but I think the idea is clear.
Note that this won't prevent an exception to be raised if you declare an indexer in your own classes. So a better way might be to check for indexers directly:
foreach (var prop in childProps)
{
if (prop.GetIndexParameters().Any()) continue;
Second note: The current code has another flaw: You should keep track of which types you already dumped and abort the recursion when you come across a type the second time. That's possibly the reason for the exception at DateTime. A DateTime has a Date property, which is - hurray - of type DateTime. And so your objtree string grows infinitly until an OutOfMemoryException or StackOverflowException is thrown.

You need to skip recursion when:
Property is a value type
Property is a string
Property value contains reference to the object from the previous recursion level (ie, ParentObject) so that you don't get a stack overflow exception
Edit: Also when property is a collection type. If you want to get creative, you can have your recursor iterate through each object in the collection and then recurse through those
This PropertyInfo recursor seems to do the trick.
[Flags]
public enum PropertyRecursionOverflowProtectionType
{
SkipSameReference,
SkipSameType
}
public class PropertyRecursionBot
{
public object ParentObject { get; set; }
public object CurrentObject { get; set; }
public PropertyInfo PropertyInfo { get; set; }
public Type ParentType { get; set; }
public int Level { get; set; }
}
public static IEnumerable<PropertyRecursionBot> GetAllProperties(object entity,
PropertyRecursionOverflowProtectionType overflowProtectionType = PropertyRecursionOverflowProtectionType.SkipSameReference)
{
var type = entity.GetType();
var bot = new PropertyRecursionBot { CurrentObject = entity };
IEnumerable<PropertyRecursionBot> GetAllProperties(PropertyRecursionBot innerBot, PropertyInfo[] properties)
{
var currentParentObject = innerBot.ParentObject;
var currentObject = innerBot.CurrentObject;
foreach (var pi in properties)
{
innerBot.PropertyInfo = pi;
var obj = pi.GetValue(currentObject);
innerBot.CurrentObject = obj;
//Return the property and value only if it's a value type or string
if (pi.PropertyType == typeof(string) || !pi.PropertyType.IsClass)
{
yield return innerBot;
continue;
}
//This overflow protection check will prevent stack overflow if your object has bidirectional navigation
else if (innerBot.CurrentObject == null ||
(overflowProtectionType.HasFlag(PropertyRecursionOverflowProtectionType.SkipSameReference) && innerBot.CurrentObject == currentParentObject) ||
(overflowProtectionType.HasFlag(PropertyRecursionOverflowProtectionType.SkipSameType) && innerBot.CurrentObject.GetType() == currentParentObject?.GetType()))
{
continue;
}
innerBot.Level++;
innerBot.ParentObject = currentObject;
foreach (var innerPi in GetAllProperties(innerBot, pi.PropertyType.GetProperties()))
{
yield return innerPi;
}
innerBot.Level--;
innerBot.ParentObject = currentParentObject;
innerBot.CurrentObject = obj;
}
}
foreach (var pi in GetAllProperties(bot, type.GetProperties()))
{
yield return pi;
}
}
Use it like this:
public class RecursionTest
{
public string StringValue { get; set; }
public int IntValue { get; set; }
public RecursionTest Test { get; set; }
public RecursionTest ParentTest { get; set; }
}
var rec1 = new RecursionTest
{
IntValue = 20,
StringValue = Guid.NewGuid().ToString()
};
rec1.Test = new RecursionTest
{
IntValue = 30,
StringValue = Guid.NewGuid().ToString(),
ParentTest = rec1
};
rec1.Test.Test = new RecursionTest
{
IntValue = 40,
StringValue = Guid.NewGuid().ToString(),
ParentTest = rec1.Test
};
foreach (var bot in GetAllProperties(rec1, PropertyRecursionOverflowProtectionType.SkipSameReference))
{
Console.WriteLine($"{new string(' ', bot.Level * 2)}{bot.PropertyInfo.Name}: {bot.CurrentObject}");
}

C# Index was outside the bounds of the array while generating Json objects

I have created a class:
internal class Movie
{
public class BaseResponse
{
public Item[] search { get; set; }
public string response { get; set; }
}
public class Item
{
public string title { get; set; }
}
I want to create n objects for search array like this:
public void Generate()
{
Movie.BaseResponse baseResponse = new Movie.BaseResponse();
baseResponse.response = "True!";
baseResponse.search = new Movie.Item[] { new Movie.Item()};
baseResponse.search[0].title = "Title one";
baseResponse.search[1].title = "Title two"; //Error accurs here****
string response = JsonConvert.SerializeObject(baseResponse);
}
but this script does not work right and it gives the following error:
Index was outside the bounds of the array
Can anyone explain how can I create n objects of search array in the Movie class?

Rather than using an array (T[]), you may be better off using a List<T>. You need to know how many items will be in an array up front (since they get allocated contiguously). You can add new items to a List at any time.
Changing your code:
internal class Movie
{
public class BaseResponse
{
public List<Item> Search { get; set; } = new List<Item>();
public string Response { get; set; }
}
public class Item
{
public string Title { get; set; }
}
}
public void Generate()
{
Movie.BaseResponse baseResponse = new Movie.BaseResponse();
baseResponse.Response = "True!";
baseResponse.Search.Add (new Movie.Item { Title = "Title One" });
baseResponse.Search.Add (new Movie.Item { Title = "Title Two" });
string response = JsonConvert.SerializeObject(baseResponse);
}
That seems to work. I get this as response:
{
"Search":[
{"Title":"Title One"},
{"Title":"Title Two"}],
"Response":"True!"
}

You've create an array with 1 item, but you're trying to access the non-existent second item.
Change the relevant line to something like:
baseResponse.search = new Movie.Item[] { new Movie.Item(), new Movie.Item() };

How to copy a List<> to another List<> with Comparsion in c#

I an having Two Lists. I want to get the matched and unmatched values based on ID and add the results to another List. I can get both of these using Intersect/Except.
But I can get only ID in the resultant variables (matches and unmatches) . I need all the properties in the Template.
List<Template> listForTemplate = new List<Template>();
List<Template1> listForTemplate1 = new List<Template1>();
var matches = listForTemplate .Select(f => f.ID)
.Intersect(listForTemplate1 .Select(b => b.ID));
var ummatches = listForTemplate .Select(f => f.ID)
.Except(listForTemplate1.Select(b => b.ID));
public class Template
{
public string ID{ get; set; }
public string Name{ get; set; }
public string Age{ get; set; }
public string Place{ get; set; }
public string City{ get; set; }
public string State{ get; set; }
public string Country{ get; set; }
}
public class Template1
{
public string ID{ get; set; }
}

If you don't want to implement IEquality for this simple task, you can just modify your LINQ queries:
var matches = listForTemplate.Where(f => listForTemplate1.Any(b => b.ID == f.ID));
and
var unmatches = listForTemplate.Where(f => listForTemplate1.All(b => b.ID != f.ID));
You might want to check for null before accessing ID, but it should work.

You are looking for the overloaded function, with the second parameter IEqualityComparer. So make your comparer ( example: http://www.blackwasp.co.uk/IEqualityComparer.aspx ), and use the same comparer in intersect / except.
And for the generic part: maybe you should have a common interface for templates e.g. ObjectWithID describing that the class have a string ID property. Or simply use dynamic in your comparer (but I think this is very-very antipattern because you can have run time errors if using for the bad type).
You also have a problem: intersecting two collections with two different types will result in a collection of Object (common parent class). Then you have to cast a lot (antipattern). I advise you to make a common abstract class/interface for your template classes, and it is working. If you need to cast the elements back, do not cast, but use the visitior pattern: http://en.wikipedia.org/wiki/Visitor_pattern
Example (good):
static void Main(string[] args)
{
// http://stackoverflow.com/questions/16496998/how-to-copy-a-list-to-another-list-with-comparsion-in-c-sharp
List<Template> listForTemplate = new Template[] {
new Template(){ID = "1"},
new Template(){ID = "2"},
new Template(){ID = "3"},
new Template(){ID = "4"},
new Template(){ID = "5"},
new Template(){ID = "6"},
}.ToList();
List<Template1> listForTemplate1 = new Template1[] {
new Template1(){ID = "1"},
new Template1(){ID = "3"},
new Template1(){ID = "5"}
}.ToList();
var comp = new ObjectWithIDComparer();
var matches = listForTemplate.Intersect(listForTemplate1, comp);
var ummatches = listForTemplate.Except(listForTemplate1, comp);
Console.WriteLine("Matches:");
foreach (var item in matches) // note that item is instance of ObjectWithID
{
Console.WriteLine("{0}", item.ID);
}
Console.WriteLine();
Console.WriteLine("Ummatches:");
foreach (var item in ummatches) // note that item is instance of ObjectWithID
{
Console.WriteLine("{0}", item.ID);
}
Console.WriteLine();
}
}
public class ObjectWithIDComparer : IEqualityComparer<ObjectWithID>
{
public bool Equals(ObjectWithID x, ObjectWithID y)
{
return x.ID == y.ID;
}
public int GetHashCode(ObjectWithID obj)
{
return obj.ID.GetHashCode();
}
}
public interface ObjectWithID {
string ID { get; set; }
}
public class Template : ObjectWithID
{
public string ID { get; set; }
public string Name { get; set; }
public string Age { get; set; }
public string Place { get; set; }
public string City { get; set; }
public string State { get; set; }
public string Country { get; set; }
}
public class Template1 : ObjectWithID
{
public string ID { get; set; }
}
Output:
Matches:
1
3
5
Ummatches:
2
4
6
Press any key to continue . . .

For comparison, this should also work (the first part is a variation on #MAV's answer):
var matches = from item in listForTemplate
join id in listForTemplate1 on item.ID equals id.ID
select item;
var unmatches = listForTemplate.Where(item => matches.All(elem => elem.ID != item.ID));
matches and unmatches will both be IEnumerable<Template> which is the type you require.
However, MAV's answer works fine so I'd go for that one.

As mentioned, Implement the IEqualityComparer<T> interface.
IEqualityComparer<T> MSDN
Then use this as an argument in your method for Except() and Intersect()
Intersect
There is a good example of how to do so on the link for the Intersect() method.

If you don't absolutely have to use LINQ, why not code something like this?
var matches = new List<Template>();
var unmatches = new List<Template>();
foreach (var entry in listForTemplate)
{
bool matched = false;
foreach (var t1Entry in listForTemplate1)
{
if (entry.ID == t1Entry.ID)
{
matches.Add(entry);
matched = true;
break;
}
}
if (!matched)
{
unmatches.Add(entry);
}
}
A disadvantage of the LINQ approach is that you're traversing the lists twice.

c# how to retrive objects as values from array

I am trying to create a simple 'inventory' system that stores items with the key being an items name, and with the remaining information being stored as a value. However, I am having difficulty figuring out how to then read the information. For example, if I have say a list of 10 items, and I want to select the items 'type' information from the key 'television' outlined below, how could I do this?
television {large, 5, 3, false, dynamic, 0.8, 20}
Hashtable myItems = new Hashtable();
protected virtual bool OnAttempt_AddItem(object args) {
object[] arr = (object[])args;
string ItemType = (string)arr[0];
string ItemName = (string)arr[1];
int ItemAmount = (arr.Length == 2) ? (int)arr[2] : 1;
int ItemACanHave = (arr.Length == 3) ? (int)arr[3] : 1;
bool ItemClear = (bool)arr[4];
string ItemEffect = (string)arr[5];
float ItemModifier = (float)arr[6];
int ItemWeight = (int)arr[7];
// enforce ability to have atleast 1 item of each type
ItemACanHave = Mathf.Max(1, ItemACanHave);
myItems[ItemName] = new object[] {ItemType, ItemAmount, ItemACanHave, ItemClear, ItemEffect, ItemModifier, ItemWeight };
return true;
}

Create an item class to encapsulate the properties:
public class InventoryItem
{
public string Name;
public string Type;
public int Amount;
public int CanHave; // you should consider renaming this - it's very unclear what this could mean
public bool Clear;
public string Effect;
public float Modifier;
public int Weight;
}
Then you can use a Dictionary to store items:
Dictionary<string, InventoryItem> inventory = new Dictionary<string, InventoryItem>();
inventory["television"] = new InventoryItem
{
Name = "television", Type = "large", Amount = 5,
CanHave = 3, Clear = false, Effect = "dynamic",
Modifier = 0.8, Weight = 20
});
And you can look it up like this:
Console.WriteLine("Type of television is: ", inventory["television"].Type);

I would suggest you to consider the possibility of more than one item of a certain type in a inventory list, i.e. two or more television sets instead of only one.
Use a base class and derived classes:
public class InventoryItem
{
public string ItemType { get; set; }
public string ItemName { get; set; }
public int ItemAmount { get; set; }
public int ItemACanHave { get; set; }
public bool ItemClear { get; set; }
public string ItemEffect { get; set; }
public float ItemModifier { get; set; }
public int ItemWeight { get; set; }
}
public class Radio : InventoryItem
{
}
public class Television : InventoryItem
{
}
// TODO: add your derived classes
Use a List<InventoryItem> to store the collection:
List<InventoryItem> InventoryItems = new List<InventoryItem>();
Modify your method (don't forget to add exception handling, as sometimes you might get different input than the one you expected in the args object):
protected virtual bool OnAttempt_AddItem(object args)
{
// TODO: handle unboxing exceptions, size of the array etc
//
try
{
object[] arr = (object[])args;
switch (arr[0].ToString().ToLower())
{
// TODO: add other types (Radio etc)
case "television":
var tv = new Television();
tv.ItemType = (string)arr[0];
tv.ItemName = (string)arr[1];
tv.ItemAmount = (arr.Length == 2) ? (int)arr[2] : 1;
tv.ItemACanHave = (arr.Length == 3) ? (int)arr[3] : 1;
tv.ItemClear = (bool)arr[4];
tv.ItemEffect = (string)arr[5];
tv.ItemModifier = (float)arr[6];
tv.ItemWeight = (int)arr[7];
// enforce ability to have atleast 1 item of each type
tv.ItemACanHave = Math.Max(1, tv.ItemACanHave);
InventoryItems.Add(tv);
break;
default:
var genericItem = new InventoryItem();
genericItem.ItemType = (string)arr[0];
genericItem.ItemName = (string)arr[1];
genericItem.ItemAmount = (arr.Length == 2) ? (int)arr[2] : 1;
genericItem.ItemACanHave = (arr.Length == 3) ? (int)arr[3] : 1;
genericItem.ItemClear = (bool)arr[4];
genericItem.ItemEffect = (string)arr[5];
genericItem.ItemModifier = (float)arr[6];
genericItem.ItemWeight = (int)arr[7];
// enforce ability to have atleast 1 item of each type
genericItem.ItemACanHave = Math.Max(1, genericItem.ItemACanHave);
InventoryItems.Add(genericItem);
break;
//handle other cases
}
return true;
}
catch (Exception ex)
{
// log the error
return false;
}
}
Retrieve the filtered items like this:
var largeTvType = inventory.InventoryItems.OfType<Television>()
// filter by type (or other criteria)
.Where(tv => tv.ItemType == "large")
// select only the property your interested in (in the case below
// it will be always "television" because that's part of the
// logic inside the OnAttempt_AddItem method's switch statement)
.Select(tv => tv.ItemType);
Still, as ChrisWue suggested in his answer, if you know that your inventory lists will be very large, I'd recommend you to use a Dictionary<string, InventoryItem>, the string key being a unique inventory item identifier. It will be faster.

How do I Find an object up the list I am iterating through

I am iterating through a List of objects of Type "prvEmployeeIncident".
The object has the following properties:
public DateTime DateOfIncident { get; set; }
public bool IsCountedAsAPoint;
public decimal OriginalPointValue;
public bool IsFirstInCollection { get; set; }
public bool IsLastInCollection { get; set; }
public int PositionInCollection { get; set; }
public int DaysUntilNextPoint { get; set; }
public DateTime DateDroppedBySystem { get; set; }
public bool IsGoodBehaviorObject { get; set; }
My List is sorted by the DateOfIncident property. I would like to find the next object up the list where IsCounted == true and change it to IsCounted = false.
One question:
1) How do I find this object up the list ?

If I understand your question correctly, you can use LINQ FirstOrDefault:
var nextObject = list.FirstOrDefault(x => x.IsCountedAsAPoint);
if (nextObject != null)
nextObject.IsCountedAsAPoint = false;

If I understand correctly this can be solved with a simple foreach loop. I don't exactly understand your emphasis on "up" as you don't really move up a list, you traverse it. Anyways, the following code snippet finds the first Incident where IsCounted is true and changes it to false. If you're starting from a given position change the for each loop to a for loop and start at i = currentIndex with the exit condition being i < MyList.Count. Leave the break statement to ensure you only modify one Incident object.
foreach (prvEmployeeIncident inc in MyList)
{
if (inc.IsCountedAsAPoint)
{
inc.IsCountedAsAPoint = false;
break;
}
}

You can use List(T).FindIndex to search up the list.
Example:
public class Foo
{
public Foo() { }
public Foo(int item)
{
Item = item;
}
public int Item { get; set; }
}
var foos = new List<Foo>
{
new Foo(1),
new Foo(2),
new Foo(3),
new Foo(4),
new Foo(5),
new Foo(6)
};
foreach (var foo in foos)
{
if(foo.Item == 3)
{
var startIndex = foos.IndexOf(foo) + 1;
var matchedFooIndex = foos.FindIndex(startIndex, f => f.Item % 3 == 0);
if(matchedFooIndex >= startIndex) // Make sure we found a match
foos[matchedFooIndex].Item = 10;
}
}
Just be sure you do not modify the list itself since that will throw an exception.