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}");
}

Compare 2 Properties of equals object

I have a class with 2 properties
public class SampleClass
{
public string Name { get; set; }
public List<Component> Components { get; set; }
}
And another class which is hold some string properties.
public class Component
{
public string Name { get; set; }
public string Age{ get; set; }
}
I have instance of this class created and added into a List
SampleClass classWithValues = new SampleClass();
var listComponent = new List<Component>();
listComponent.add(new Component{Name = "Random string",Age = "31"})
classWithValues.Components = listComponent;
classWithValues.Name = "TestName"
var listWithObjectClass = new List<SampleClass>();
listWithObjectClass.add(classWithValues);
Then i made a new instance of the SampleClass class and add exactly the same value into the properties :
SampleClass classWithValues1 = new SampleClass();
var listComponent1 = new List<Component>();
listComponent1.add(new Component{Name = "Random string",Age = "31"})
classWithValues1.Components = listComponent1;
classWithValues1.Name = "TestName";
And here is coming the strange part :
if I compare the property Names inside the list with the second instance of the Sample class with the new instance of the same class:
bool alreadyExists = listWithObjectClass.Any(x => x.Name == classWithValues1 .Name);
the result is true BUT
if I compare the List properties
bool alreadyExists = listWithObjectClass.Any(x => x.Components == classWithValues1.Components);
the result is false ?!
Can someone please give some information about this behavior.

Sorry my first answer was not quite right...
In order to get alreadyExist to be true you need to put in place property comparison in your classes as otherwise the equality comparison performed is the default reference comparison. Your objects contains the same property values but are actually different instances... The default equality comparison for objects is comparing references not content.
Try this...
void Main()
{
SampleClass classWithValues = new SampleClass();
var listComponent = new Components();
listComponent.Add(new Component{Name = "Random string",Age = "31"});
classWithValues.Components = listComponent;
classWithValues.Name = "TestName";
var listWithObjectClass = new List<SampleClass>();
listWithObjectClass.Add(classWithValues);
SampleClass classWithValues1 = new SampleClass();
var listComponent1 = new Components();
listComponent1.Add(new Component{Name = "Random string",Age = "31"});
classWithValues1.Components = listComponent1;
classWithValues1.Name = "TestName";
bool alreadyExists = listWithObjectClass.Any(x => x.Components.Equals(classWithValues1.Components));
}
public class SampleClass
{
public string Name { get; set; }
public Components Components { get; set; }
}
public class Component : IEquatable<Component>
{
public string Name { get; set; }
public string Age{ get; set; }
public bool Equals(Component otherComponent)
{
return Name == otherComponent.Name && Age == otherComponent.Age;
}
}
public class Components :List<Component>, IEquatable<Components>
{
public bool Equals(Components otherComponents)
{
if(this.Count!= otherComponents.Count) return false;
return this.TrueForAll(a=> otherComponents.Any(q=>q.Equals(a)))
&& otherComponents.TrueForAll(a=> this.Any(q=>q.Equals(a)));
}
}

The first comparison is about comparing the value of the two string. However, the second comparison is about Comparing two different object which their reference are different. Indeed, for the second comparison, compare their hashCode. To watch this, you can call .GetHashCode() for these two objects.
listComponent.GetHashCode() == listComponent1.GetHashCode() // false
listComponent[0].GetHashCode() == listComponent1[0].GetHashCode() // false

Updating Custom Class in List<T>

I am trying to update a List which is a List of Interfaces to concrete classes.
I add to the List each Market type i am interested in, for this Example these Markets are A and B
I loop over all the markets, (sample provided with 3 markets A B & C, we are only interested in A and B) And determine which is of interest to us.
Once found we pass this to an extraction method too do its work and create an instance of the Correct Market_ class type.
This all works fine, but when i try to update the list with the Updates it does not get reflected in the List.
Code below, any Suggestions?
Thanks
public class Test
{
public Test()
{
TheMarkets MarketsToUpdate = new TheMarkets();
List<SpecificCompanyMarket> lstMarks = new List<SpecificCompanyMarket>();
lstMarks.Add(new SpecificCompanyMarket(1234, "A", "Some HTML DATA HERE"));
lstMarks.Add(new SpecificCompanyMarket(5874, "B", "Some HTML DATA HERE"));
lstMarks.Add(new SpecificCompanyMarket(2224, "C", "Some HTML DATA HERE"));
foreach (var item in lstMarks)
{
if (MarketsToUpdate.IsMarketWeAreInterestedIn(item.MarketName))
{
ITheMarkets MarkToUpdate = ExtractMarketData(item);
var obj = MarketsToUpdate.MarketsWeAreInterestedIn.FirstOrDefault(x => x.MarketName() == "A");
if (obj != null)
{
obj = MarkToUpdate;
}
}
}
//Look At MarketsToUpdate Now and the item has not changed, still original values
//I was expecting to see the new values for the fields in A, not the default 0's
}
public ITheMarkets ExtractMarketData(SpecificCompanyMarket item)
{
ITheMarkets market = null;
if (item.MarketName.ToUpper() == "A")
{
Market_A marketType = new Market_A();
marketType.SomeValue1 = 123;
marketType.SomeValue2 = 158253;
market = marketType;
}
//Other Market extractions here
return market;
}
}
public class SpecificCompanyMarket
{
public int MarketId { get; set; }
public string MarketName { get; set; }
public string MarketDataHTML { get; set; }
public SpecificCompanyMarket(int MID, string MName, string MData)
{
MarketId = MID;
MarketName = MName;
MarketDataHTML = MData;
}
}
public class TheMarkets
{
public List<ITheMarkets> MarketsWeAreInterestedIn = new List<ITheMarkets>();
public TheMarkets()
{
Market_A A = new Market_A();
Market_B B = new Market_B();
MarketsWeAreInterestedIn.Add(A);
MarketsWeAreInterestedIn.Add(B);
}
public bool IsMarketWeAreInterestedIn(string strMarketName)
{
bool blnRetVal = false;
foreach (var item in MarketsWeAreInterestedIn)
{
if (item.MarketName().ToUpper().Trim().Equals(strMarketName.ToUpper().Trim()))
{
blnRetVal = true;
break;
}
}
return blnRetVal;
}
}
public interface ITheMarkets
{
string MarketName();
}
public class Market_A : ITheMarkets
{
public string LabelType { get; private set; }
public double SomeValue1 { get; set; }
public double SomeValue2 { get; set; }
public double SomeValue3 { get; set; }
public Market_A()
{
LabelType = "A";
}
public string MarketName()
{
return LabelType;
}
}
public class Market_B : ITheMarkets
{
public string LabelType { get; private set; }
public List<string> SomeList { get; set; }
public double SomeValue { get; set; }
public Market_B()
{
LabelType = "B";
}
public string MarketName()
{
return LabelType;
}
}

This is a short example to get you going. Loop through your list, find the object you want to update, create a new object of that type and then find the original objects index in the list and overwrite it in place. You are essentially just replacing the object in the list with a new one not mutating the existing one.
foreach (var item in lstMarks)
{
//your code to get an object with data to update
var yourObjectToUpdate = item.GetTheOneYouWant();
//make updates
yourObjectToUpdate.SomeProperty = "New Value";
int index = lstMarks.IndexOf(item);
lstMarks[index] = yourObjectToUpdate;
}

You are extracting an obj from marketWeAreInterestedIn list using LINQ's firstOrDefault extension. This is a new object and not a reference to the obj in that list. Therefore, no updates will be reflected in the object inside that list. Try using 'indexof'

You are not storing "list of interfaces" in your list. List<T> stores an array of pointers to objects that support T interface. Once you enumerate (with Linq in your case) your list, you copy a pointer from list, which is not associated with list itself in any way. It is just a pointer to your instance.
To do what you want, you will have to build new list while enumerating the original one, adding objects to it, according to your needs, so the second list will be based on the first one but with changes applied that you need.
You can also replace specific instance at specific index instead of building new list in your code, but to do this you will need to enumerate your list with for loop and know an index for each item:
list[index] = newvalue;
But there is a third solution to update list item directly by Proxying them. This is an example
class ItemProxy : T { public T Value { get; set; } }
var list = new List<ItemProxy<MyClass>>();
list.Insert(new ItemProxy { Value = new MyClass() });
list.Insert(new ItemProxy { Value = new MyClass() });
list.Insert(new ItemProxy { Value = new MyClass() });
foreach(var item in list)
if(item // ...)
item.Value = new MyClass(); // done, pointer in the list is updated.
Third is the best case for perfomance, but it will be better to use this proxying class for something more than just proxying.

Value cannot be null. Error

I have an error with the method below where I am trying to add data from a combobox to a datagrid and then after I add the data I want to calculate the total amount of the 'ItemSellingPrice' and display that amount in a label.
using (TruckServiceClient TSC = new TruckServiceClient())
{
var item = cmbAddExtras.SelectedItem as ExtraDisplayItems;
if (item != null)
{
var displayItem = new List<ExtraDisplayItems>
{
new ExtraDisplayItems
{
displayItems = item.displayItems,
ItemId = item.ItemId,
ItemCode = item.ItemCode,
ItemDescription = item.ItemDescription,
ItemSellingPrice = item.ItemSellingPrice,
}
};
dgAddExtras.Items.Add(item);
var subTotalExtras = item.displayItems.Sum(x => x.ItemSellingPrice.GetValueOrDefault(0)); //Here
lblSubTotalExtrasAmount.Content = "R" + subTotalExtras;
}
}
The error that I get is:
Value cannot be null.
Does anyone have any ideas why this is happening?
EDIT: This is where I set the displayItems in my class
public class ExtraDisplayItems
{
public List<ExtraDisplayItems> displayItems;
public int ItemId { get; set; }
public string ItemCode { get; set; }
public string ItemDescription { get; set; }
public double? ItemSellingPrice { get; set; }
}

Thanks to Gert Arnold, the actual issue is that the item.displayItems is null (so not inside the lambda, since that works perfectly fine).
Some proof. This gets your exact error message:
double?[] x = null;
double? sum = x.Sum(y => y);
(The reason you don't get a NullReferenceException is that you actually call a static method (an extension method), so technically the reference isn't null but the argument is).
You should check where you set item.displayItems or prevent calling Sum on a item.displayItems with value null.

How to convert Null to String with Linq to Entity

I'm trying to use reflection within a linq query to change a Decimal Null value to a string value. My code produce this error;
"Object of type System.String cannot be converted to type System.Nullable System.Decimal"
Thanks for your help.
public class ReportData
{
public IEnumerable<SASF> GetLongReportData(string commSubGp)
{
var context = new Entities();
string myDate = "2014-03-18";
DateTime date = Convert.ToDateTime(myDate);
var result = new List<SASF>();
if (commSubGp == "F00")
{
result = (from a in context.SASF
where a.RDate == date &&
a.COMM_SGP.CompareTo("F00") <= 0
orderby a.Conmkt, a.MKTTITL descending
select a).ToList();
//Here I'm trying to use reflection to loop through the object and set any value that's null to string value
result.ForEach(reflect =>
{
reflect.GetType().GetProperties().ToList().ForEach(p =>
{
var checkValue = p.GetValue(reflect, null);
if (checkValue == null)
{
p.SetValue(reflect, "non-reportable", null);
}
});
});
return result.ToList();
}
return results;
}
}

Since your property type is Decimal? the string "non-reportable" can not be converted to Decimal and the value fails to set. You could set it to zero however:
p.SetValue(reflect, Decimal.Zero, null)
Or any decimal value for that matter.
p.SetValue(reflect, Decimal.MinValue, null)
p.SetValue(reflect, Decimal.MaxValue, null)
Not knowing what the data is to be used for in the end I have no idea whether this would be appropriate or not.

Using reflection to do this probably isn't the best solution as it is quite an expensive process. Utilising the method below allows you to be specific and output the data in a way you see fit (although you could do this on the DB side too).
Without knowing the structure of the SASF class I have just created a pseudo class.
This of course requires you to specifically map each field to your stringified class. You might be able to use some tool like AutoMapper (https://github.com/AutoMapper/AutoMapper) to do this for you.
public class ReportData
{
public IEnumerable<SASFStringified> GetLongReportData(string commSubGp)
{
var context = new Entities();
string myDate = "2014-03-18";
DateTime date = Convert.ToDateTime(myDate);
var result = new List<SASF>();
if (commSubGp == "F00")
{
result = (from a in context.SASF
where a.RDate == date &&
a.COMM_SGP.CompareTo("F00") <= 0
orderby a.Conmkt, a.MKTTITL descending
select a).ToList();
var stringifiedResult = new List<SASFStringified>();
foreach (var sasf in result)
{
stringifiedResult.Add(new SASFStringified
{
ID = sasf.ID,
Field1 = sasf.Field1.HasValue ? sasf.Field1.Value.ToString() : "non-reportable",
Field2 = sasf.Field2.HasValue ? sasf.Field2.Value.ToString() : "non-reportable",
DateField = sasf.DateField.ToShortDateString()
});
}
return stringifiedResult;
}
return results;
}
}
public class SASF
{
public int ID { get; set; }
public decimal? Field1 { get; set; }
public decimal? Field2 { get; set; }
public DateTime DateField { get; set; }
}
public class SASFStringified
{
public int ID { get; set; }
public string Field1 { get; set; }
public string Field2 { get; set; }
public string DateField { get; set; }
}