I would like to make a query by using lambda select,
Like below:
public class Foo{
public int Id {get;set;}
public string Name {get;set;}
public string Surname {get;set;}
}
var list = new List<Foo>();
var temp = list.Select(x=> x("Name"),("Surname"));
The property name needs to be sent as a string,
I dont know how to use, I have given it for being a example.
is it possible?
Edit:
Foo list :
1 A B
2 C D
3 E F
4 G H
I don't know type of generic list, I have property name such as "Name", "Surname"
I want to be like below:
Result :
A B
C D
E F
G H
The following code snippet shows 2 cases. One filtering on the list, and another creating a new list of anonymous objects, having just Name and Surname.
List<Foo> list = new List<Foo>();
var newList = list.Select(x=> new {
AnyName1 = x.Name,
AnyName2 = x.Surname
});
var filteredList = list.Select(x => x.Name == "FilteredName" && x.Surname == "FilteredSurname");
var filteredListByLinq = from cust in list
where cust.Name == "Name" && cust.Surname == "Surname"
select cust;
var filteredByUsingReflection = list.Select(c => c.GetType().GetProperty("Name").GetValue(c, null));
Interface
If you have access to the types in question, and if you always want to access the same properties, the best option is to make the types implement the same interface:
public interface INamable
{
string Name { get; }
string Surname { get; }
}
public class Foo : INamable
{
public int Id { get; set; }
public string Name { get; set; }
public string Surname { get; set; }
}
This will preserve type safety and enable queries like this one:
public void ExtractUsingInterface<T>(IEnumerable<T> list) where T : INamable
{
var names = list.Select(o => new { Name = o.Name, Surname = o.Surname });
foreach (var n in names)
{
Console.WriteLine(n.Name + " " + n.Surname);
}
}
If, for some reason, you can't alter the original type, here are two more options.
Reflection
The first one is reflection. This is Mez's answer, i'll just rephrase it with an anonymous type like in the previous solution (not sure what you need exactly):
public void ExtractUsingReflection<T>(IEnumerable<T> list)
{
var names = list.Select(o => new
{
Name = GetStringValue(o, "Name"),
Surname = GetStringValue(o, "Surname")
});
foreach (var n in names)
{
Console.WriteLine(n.Name + " " + n.Surname);
}
}
private static string GetStringValue<T>(T obj, string propName)
{
return obj.GetType().GetProperty(propName).GetValue(obj, null) as string;
}
Dynamic
The second uses dynamic:
public void ExtractUsingDynamic(IEnumerable list)
{
var dynamicList = list.Cast<dynamic>();
var names = dynamicList.Select(d => new
{
Name = d.Name,
Surname = d.Surname
});
foreach (var n in names)
{
Console.WriteLine(n.Name + " " + n.Surname);
}
}
With that in place, the following code:
IEnumerable<INamable> list = new List<Foo>
{
new Foo() {Id = 1, Name = "FooName1", Surname = "FooSurname1"},
new Foo() {Id = 2, Name = "FooName2", Surname = "FooSurname2"}
};
ExtractUsingInterface(list);
// IEnumerable<object> list... will be fine for both solutions below
ExtractUsingReflection(list);
ExtractUsingDynamic(list);
will produce the expected output:
FooName1 FooSurname1
FooName2 FooSurname2
FooName1 FooSurname1
FooName2 FooSurname2
FooName1 FooSurname1
FooName2 FooSurname2
I'm sure you can fiddle with that and get to what you are trying to achieve.
var temp = list.Select(x => x.Name == "Name" && x.Surname == "Surname");
var temp = list.Select(x => new {Name = x.Name, Surname = x.Surname});
Related
I have a list with two elements
element 1:
no:1,
vendor: a,
Description: Nice,
price :10
element 2:
no:1
vendor:a,
Description: Nice,
price:20
i have lot more fields in list elements so i cannot use new to sum the price
if everything is same except price i need to combine two elements into a single element by summing price.
o/p element 1:
no:1,
vendor:a,
Description:Nice,
price:30
Tried below one but not sure how to sum the price and return the entire fields with out using new
list.GroupBy(y => new { y.Description,y.vendor, y.no})
.Select(x => x.ToList().OrderBy(t => t.Price)).FirstOrDefault()
If you prefer LINQ query expressions:
var groupedElements = from element in elements
group element by new
{
element.no,
element.Description,
element.vendor
}
into grouped
select new {grouped, TotalPrice = grouped.Sum(x => x.price)};
The total price is calculated with the final .Sum method call on the grouped elements.
Try following :
class Program
{
static void Main(string[] args)
{
List<Element> elements = new List<Element>() {
new Element() { no = 1, vendor = "a", Description = "Nice", price = 10},
new Element() { no = 1, vendor = "a", Description = "Nice", price = 20}
};
List<Element> totals = elements.GroupBy(x => x.no).Select(x => new Element()
{
no = x.Key,
vendor = x.FirstOrDefault().vendor,
Description = x.FirstOrDefault().Description,
price = x.Sum(y => y.price)
}).ToList();
}
}
public class Element
{
public int no { get;set; }
public string vendor { get;set; }
public string Description { get;set; }
public decimal price { get;set; }
}
Try following using Clone
using System;
using System.Collections.Generic;
using System.Collections;
using System.Linq;
using System.Text;
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
List<Element> elements = new List<Element>() {
new Element() { no = 1, vendor = "a", Description = "Nice", price = 10},
new Element() { no = 1, vendor = "a", Description = "Nice", price = 20}
};
var groups = elements.GroupBy(x => x.no).ToList();
List<Element> totals = new List<Element>();
foreach (var group in groups)
{
Element newElement = (Element)group.FirstOrDefault().Clone();
newElement.price = group.Sum(x => x.price);
totals.Add(newElement);
}
}
}
public class Element : ICloneable
{
public int no { get;set; }
public string vendor { get;set; }
public string Description { get;set; }
public decimal price { get;set; }
public object Clone()
{
return this;
}
}
}
Willy-nilly you have to create Key which has 3 properties;
If you don't like the current solution with anonymous class
list
.GroupBy(y => new {
y.Description,
y.vendor,
y.no}
)
...
You can do it in different way, e.g. with a help of unnamed tuple:
list
.GroupBy(y => Tuple.Create(
y.Description,
y.vendor,
y.no)
)
...
Or named tuple (see https://learn.microsoft.com/en-us/dotnet/csharp/tuples for details):
list
.GroupBy(y => (
Description : y.Description,
vendor : y.vendor,
no : y.no)
)
...
Or even tailored class. What's matter the most, however, is that you can't just get First item from the group
but should create a new instance. Another issue is premature materialization: .ToList() when you then get rid of this new born list and keep on querying with .OrderBy(...)
var result = result
.GroupBy(y => new {
y.Description,
y.vendor,
y.no}
)
.Select(group => MyObject() { //TODO: put the right syntax here
Description = group.Key.Description,
vendor = group.Key.vendor,
no = group.Key.no,
price = group.Sum(item => item.price) // you want to sum prices, right?
});
You need to create a custom IEqualityComparer, which when passed into the GroupBy clause, will group the items according to your needs.
Asuming the following sample class:
public class Element
{
public int no { get; set; }
public string vendor { get; set; }
public string Description { get; set; }
public decimal price { get; set; }
}
You can implement the following IEqualityComparer which using Reflection will compare every Propertypresent in the Element class except the ones defined in the Linq Where clause, in this case "price". Bear in mind further customizations could be required.
public class ElementComparer : IEqualityComparer<Element>
{
public bool Equals(Element a, Element b) => typeof(Element).GetProperties()
.Where(p => p.Name != "price")
.All(p => p.GetValue(a).Equals(p.GetValue(b)));
public int GetHashCode(Element obj) => obj.no.GetHashCode();
}
Then simply group them this way
list.GroupBy(x => x, new ElementComparer()).Select(g =>
{
// Here you need to either clone the first element of the group like
// #jdweng did, or create a new instance of Element like I'm doing below
Element element = new Element();
foreach (var prop in element.GetType().GetProperties())
{
if (prop.Name == "price")
{
prop.SetValue(element, g.Sum(y => y.price));
}
else
{
prop.SetValue(element, prop.GetValue(g.First()));
}
}
return element;
});
I think what you're trying to do is write dynamic code that groups by all properties except for the property you want to sum. This solution should work, though I loath to use reflection. A more performant method would be to use expression trees to generate an aggregation delegate that you reuse, but that is very involved. This should do the trick:
Edit: There's another answer that also seems to work. Mine assumes you will want to do this with any collection regardless of type. Doesn't require ICloneable or a type-specific IEqualityComparer<T>, though, as a slight trade-off, the other one will likely perform better in very large datasets.
static T[] GetGroupSums<T>(IEnumerable<T> collection, string sumPropertyName) where T : new()
{
//get the PropertyInfo you want to sum
//var sumProp = (PropertyInfo)((MemberExpression)((UnaryExpression)memberExpression.Body).Operand).Member;
var sumProp = typeof(T).GetProperty(sumPropertyName);
//get all PropertyInfos that are not the property to sum
var groupProps = typeof(T).GetProperties().Where(x => x != sumProp).ToArray();
//group them by a hash of non-summed properties (I got this hash method off StackExchange many years back)
var groups = collection
.GroupBy(x => GetHash(groupProps.Select(pi => pi.GetValue(x)).ToArray()))
.Select(items =>
{
var item = new T();
var firstItem = items.First();
//clone the first item
foreach (var gp in groupProps)
{
gp.SetValue(item, gp.GetValue(firstItem));
}
//Get a decimal sum and then convert back to the sum property type
var sum = items.Sum(_item => (decimal)Convert.ChangeType(sumProp.GetValue(_item), typeof(decimal)));
sumProp.SetValue(item, Convert.ChangeType(sum, sumProp.PropertyType));
//If it will always be int, just do this
//var sum = items.Sum(_item => (int)sumProp.GetValue(_item));
//sumProp.SetValue(item, sum);
return item;
});
return groups.ToArray();
}
//I got this hash method off StackExchange many years back
public static int GetHash(params object[] args)
{
unchecked
{
int hash = 17;
foreach (object arg in args)
{
hash = hash * 23 + arg.GetHashCode();
}
return hash;
}
}
Use it like this:
List<Element> elements = new List<Element>() {
new Element() { no = 1, vendor = "a", Description = "Nice", price = 10},
new Element() { no = 2, vendor = "a", Description = "Nice", price = 15},
new Element() { no = 2, vendor = "b", Description = "Nice", price = 10},
new Element() { no = 1, vendor = "a", Description = "Nice", price = 20}
};
var groups = GetGroupSums(elements, nameof(Element.price));
I have 2 lists of a specific type, in this case it is List. In the class DataDictionary there is a property called TableName. I have 2 lists with the same type I am trying to compare. I have other properties aswell which I need to hold association with that specific TableName so I can't just compare them separately.
I need to find a way to compare the TableName in 2 different lists of DataDictionary and then find which ones they don't have in common. From there I then need to compare all the other properties against the 2 items in each list with the same TableName.
I have tried to use the Except IEnumerate solution which works if you just compare the strings directly but I don't know how to keep the association with the object.
List<DataDictionary> ColumnsDataDict = daDD.getTablesandColumnsDataDictionary();
List<DataDictionary> ColumnsWizard = daWiz.getColumnsWizard();
var newlist = ColumnsWizard.Except(ColumnsDataDict);
foreach(DataDictionary item in newlist)
{
Console.WriteLine(item.TableName);
}
Here is the DataDictionary class:
public string TableName { get; set; }
public string Description { get; set; }
public string TableID { get; set; }
public string ColumnDesc { get; set; }
public string ColumnName { get; set; }
This directly compares the objects, but I just want to compare the TableName property in my DataDictionary class. I want this to then get a list of objects that doesn't have the same table name in each list. Any help is appreciated, thanks!
I don't believe your problem can be solved with LINQ alone and there for I would recommend using a good old loop.
If you want to compare two lists, you will have to use two loops nested in one another.
Like this:
public class Program
{
public static void Main()
{
var listA = new List<Foo>() {
new Foo() { TableName = "Table A", Value = "Foo 1" },
new Foo() { TableName = "Table B", Value = "Foo 1" },
};
var listB = new List<Foo>() {
new Foo() { TableName = "Table A", Value = "Foo 10" },
new Foo() { TableName = "Table C", Value = "Foo 12" },
};
foreach (var itemA in listA)
{
foreach (var itemB in listB)
{
if (itemA.TableName == itemB.TableName)
{
Console.WriteLine($"ItemA's Value: {itemA.Value}");
Console.WriteLine($"ItemB's Value: {itemB.Value}");
}
}
}
}
}
public class Foo
{
public string TableName { get; set; }
public string Value { get; set; }
}
At the position where I am printing the values of itemA and itemB you can compare your objects and find the difference between them.
So instead of:
Console.WriteLine($"ItemA's Value: {itemA.Value}");
Console.WriteLine($"ItemB's Value: {itemB.Value}");
Maybe something like this:
if (itemA.Value != itemB.Value) //extend the `if` with all the properties you want to compare
{
Console.WriteLine($"ItemA's Value isn't equal to ItemB's Value");
}
If you need to check if listA doesn't have an entry in listB then you can extend the inner loop like this:
foreach (var itemA in listA)
{
var found = false;
foreach (var itemB in listB)
{
if (itemA.TableName == itemB.TableName)
{
found = true;
}
}
if (found == false)
{
Console.WriteLine("ItemA's TableName wasn't found in listB");
}
}
SOLUTION:
// Merges both objects
List<DataDictionary> duplicatesRemovedLists = ColumnsDataDict.Concat (ColumnsWizard).ToList ();
// Removes common objects based on its property value (eg: TableName)
foreach (var cddProp in ColumnsDataDict) {
foreach (var cwProp in ColumnsWizard) {
if ((cddProp.TableName == cwProp.TableName)) {
duplicatesRemovedLists.Remove (cddProp);
duplicatesRemovedLists.Remove (cwProp);
}
}
}
// Prints expected output
foreach (DataDictionary item in duplicatesRemovedLists) Console.WriteLine (item.TableName);
You can use several LINQ methods implementing a customer IEqualityComparer.
For instance having a comparer for the property TableName:
public class TableNameEqualityComparer : IEqualityComparer<DataDictionary>
{
public bool Equals(DataDictionary x, DataDictionary y)
{
if (x == null && y == null)
{
return true;
}
return x != null && y != null && x.TableName == y.TableName;
}
public int GetHashCode(DataDictionary obj)
{
return obj?.TableName?.GetHashCode() ?? 0;
}
}
Two instances returning true for the Equals method must return
the same value for GetHashCode.
Just make an instance of your custom comparer.
var listA = new List<DataDictionary>()
{
new DataDictionary() {TableName = "Table A"},
new DataDictionary() {TableName = "Table B"},
};
var listB = new List<DataDictionary>()
{
new DataDictionary() {TableName = "Table A"},
new DataDictionary() {TableName = "Table C"},
};
var tableNameComparer = new TableNameEqualityComparer();
And then use it with different LINQ methods:
// A - B
var listAExceptB = listA.Except(listB, tableNameComparer);
Assert.Collection(listAExceptB,
x => Assert.Equal("Table B", x.TableName));
// B - A
var listBExceptA = listB.Except(listA, tableNameComparer);
Assert.Collection(listBExceptA,
x => Assert.Equal("Table C", x.TableName));
// A ∩ B
var listIntersect = listA.Intersect(listB, tableNameComparer);
Assert.Collection(listIntersect,
x => Assert.Equal("Table A", x.TableName));
// A ∪ B
var listUnion = listA.Union(listB, tableNameComparer);
Assert.Collection(listUnion,
x => Assert.Equal("Table A", x.TableName),
x => Assert.Equal("Table B", x.TableName),
x => Assert.Equal("Table C", x.TableName));
I'm writing new api call for my android app, I want to retrieve data from dynamic table, I mean when user select "A" button from Andriod I want to retrieve data from "A" table and if "B" is click , retrieve data from "B" table. Someone help me to find the possible solution.
I want to replace with variable for "JBCTNRITEMs" from entities.JBCTNRITEMs (table-name)
var query = (from jbct in entities.JBCTNRITEMs
where jbid.Contains(jbct.jbid.ToString()) && boxid.Contains(jbct.TrackingNo.ToString())
select jbct).ToArray();
int id = 0;
if (query.Length > 0)
{
id = (query[0].id);
}
return id;
Here are the two different possibilities as an example
if (module.ToLower() == "module-a")
{
var imageinfo = (from jb in entities.TableA.AsEnumerable()
where scanID.Contains(jb.aid.ToString())
select jb).ToArray();
InsertGENIMAGE(userID, scanID, FilePath, imageinfo, "AIMAGE");
}
else if (module.ToLower() == "module-b")
{
var imageinfo = (from jb in entities.TableB.AsEnumerable()
where scanID.Contains(jb.bid.ToString())
select jb).ToArray();
InsertGENIMAGE(userID, scanID, FilePath, imageinfo, "BIMAGE");
}
Here, query stores what you are you trying to select. As long as you are trying to select same type or same anonymous type, it will work.
Here is a simple example:
class Test1
{
public int ID { get; set; }
public string Name { get; set; }
}
class Test2
{
public int ID { get; set; }
public string Name { get; set; }
}
var test1Lst = new List<Test1>
{
new Test1() { ID = 1, Name = "Jitendra" },
new Test1() { ID = 2, Name = "Jahnavi" }
};
var test2Lst = new List<Test2>
{
new Test2() { ID = 1, Name = "Aaditri" },
new Test2() { ID = 2, Name = "Pankaj" }
};
var test = false;
var query = test ? (from t in test1Lst select new { ID = t.ID, Name = t.Name }) : (from t in test2Lst select new { ID = t.ID, Name = t.Name });
// Put whatever condition you want to put here
query = query.Where(x => x.ID == 1);
foreach(var t1 in query)
{
Console.WriteLine(t1.ID + " " + t1.Name);
}
I guess in this case I would suggest to use a generic method :
private T GetMeTheFirstEntry<T>(Expression<Func<T, bool>> filter) where T : class
{
return entities.GetTable<T>().FirstOrDefault(filter);
}
The GetTable will allow you to interchange the tableA and tableB. You would call it the following way:
TableA tableA_entity = GetMeTheFirstEntry<TableA>(jb => scanID.Contains(jb.aid.ToString()));
TableB tableB_entity = GetMeTheFirstEntry<TableB>(jb => scanID.Contains(jb.bid.ToString()));
If the filtering was successfull, then the retrieved object will not be null and you can use it:
int a_id = tableA_entity.aid;
Can I perform a select using ternary operator to get an attribute from object inside a list?
Here is my model:
public class Xpto
{
public List<Son> Sons { get; set; }
}
public class Son
{
public string Names { get; set; }
}
And here i would like to get "Name" attribute for each son that i have:
var result = (from a in mylist
select new
{
sonsNames = a.Sons == null : <What should i put here?>
}).ToList<object>();
I've tried Sons.ToString() but it prints an object reference.
I would like to have a string list in "sonsNames" and each name separeted by a ','. Example: sonsName: 'george, john'.
what about this ?
//set up a collection
var xptos = new List<Xpto>()
{ new Xpto()
{ Sons = new List<Son>
{ new Son() { Names = "test1" },
new Son() { Names = "test2" }
}
},
new Xpto()
{
Sons = new List<Son> {
new Son() { Names = "test3" }
}
}};
//select the names
var names = xptos.SelectMany(r => r.Sons).Where(k => k.Names != null)
.Select(r => r.Names + ",") .ToList();
names.ForEach(n => Console.WriteLine(n));
Here's more info on SelectMany()
I'm trying to figure out how best to compare and merge two List<T> with a new List<T> being generated that compares multiple properties within each object.
class Account
{
public Account() { }
public string ID { get; set; }
public string Name { get; set; }
public string Value { get; set; }
}
List<Account> Mine = new List<Account>();
List<Account> Yours = new List<Account>();
List<Account> Ours = new List<Account>();
Account m1 = new Account(){ ID = null, Name = "C_First", Value = "joe" };
Account m2 = new Account(){ ID = null, Name = "C_Last", Value = "bloggs" };
Account m3 = new Account(){ ID = null, Name = "C_Car", Value = "ford" };
Mine.Add(m1);
Mine.Add(m2);
Mine.Add(m3);
Account y1 = new Account(){ ID = "1", Name = "C_First", Value = "john" };
Account y2 = new Account(){ ID = "2", Name = "C_Last", Value = "public" };
Yours.Add(y1);
Yours.Add(y2);
The resulting List<Account> Ours would have the following List<Account> objects:
{ ID = "1", Name = "C_First", Value = "joe" };
{ ID = "2", Name = "C_Last", Value = "bloggs" };
{ ID = null, Name = "C_Car", Value = "ford" };
I need to figure out how best to compare the ID and Value properties between both List<Account> objects where the List<Account> Yours ID takes precedence over the List<Account> Mine and the List<Account> Mine Value takes precedence over List<Account> Yours along with any object that's not in List<Account> Yours being added as well.
I've tried the following:
Ours = Mine.Except(Yours).ToList();
which results in List<Ours> being empty.
I've read this post Difference between two lists in which Jon Skeet mentions using a custom IEqualityComparer<T> to do what I need but I'm stuck on how to create an IEqualityComparer<T> that compares more than 1 property value.
Not sure if it can be done in "pue" LINQ, but a bit of procedural code would do the trick:
var dict = Yours.ToDictionary(y => y.Name);
foreach (var m in Mine) {
Account y;
if (dict.TryGetValue(m.Name, out y))
Ours.Add(new Account { ID = y.ID, Name = m.Name, Value = m.Value });
else
Ours.Add(m);
}
After that, printing Ours...
foreach (var o in Ours)
Console.WriteLine("{0}\t{1}\t{2}", o.ID, o.Name, o.Value);
...gives the following result:
1 C_First joe
2 C_Last bloggs
C_Car ford
Try this:
var index = Mine.ToDictionary(x => x.Name);
foreach(var account in Yours)
{
if(index.ContainsKey(account.Name))
{
var item = index[account.Name];
if(item.ID == null)
item.ID = account.ID;
}
index.Add(account.Name, account);
}
Ours = index.Values.ToList();
try this code for IEqualityComparer:
public class D : IEqualityComparer<Account>
{
public bool Equals(Account x, Account y)
{
return x.ID == y.ID && x.Value==y.Value;
}
public int GetHashCode(Account obj)
{
return obj.ID.GetHashCode() ^ obj.Value.GetHashCode();
}
}
used like this:
Ours = Mine.Except(Yours, new D()).ToList();