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How to select specific fields from dynamic list using LINQ

I am trying to get the some specific fields from dynamic object with is actually a list of any class, this class contains various fields out of those fields I want to select some specific fields using LINQ, The fields which I want to select is also passing by the user. Below is the code that I have tried using System.Linq.Dynamic.
using System.Linq;
using System.Text;
using System.Linq.Expressions;
using System.Linq.Dynamic;
using System.Collections;
private void Test_Click(object sender, EventArgs e)
{
List<RateInfo> lst = new List<RateInfo>();
lst.Add(new RateInfo() { id_country = "IND", id_state = 1, rate = 2.3f });
lst.Add(new RateInfo() { id_country = "IND", id_state = 2, rate = 1.1f });
lst.Add(new RateInfo() { id_country = "IND", id_state = 3, rate = 5.2f });
lst.Add(new RateInfo() { id_country = "IND", id_state = 4, rate = 6.5f });
GetDynamicData(lst, new List<string>() { "id_country", "id_state" });
}
private void GetDynamicData(dynamic list, List<string> fetchFields)
{
var data = ((IEnumerable)list).Cast<dynamic>()
.Select(r => new { r }).AsQueryable();
StringBuilder s = new StringBuilder();
//This is for test only.
//It works, the value of "id_state" and "id_state" getting appended
foreach (var item in data)
{
s.Append(item.r.id_state);
s.Append(",");
s.Append(item.r.id_country);
}
//-----------------------------------------------------
//Select the specific field data from dynamic list
StringBuilder fields = new StringBuilder();
fields.Append("new (");
foreach (var fld in fetchFields)
{
fields.Append("r." + fld);
fields.Append(",");
}
fields.Remove(fields.Length - 1, 1);
fields.Append(")");
//This does not work throws error
//"No property or field 'id_country' exists in type 'Object'"
IQueryable iq = data.Select(fields.ToString());
//For test only to check the value of selected fields
foreach (dynamic item in iq)
{
s.Append(item.id_state);
s.Append(",");
s.Append(item.id_country);
}
}

you can hughly simplify your GetDynamicData method both specifying explicit list type (GetDynamicData(IList<RateInfo> list, ...)) and leaving the list item type generic, in order to reuse the method; with this last approach in mind, you can rewrite the GetDynamicData as follows, obtaining the desired output:
private void GetDynamicData<T>(IEnumerable<T> list, List<string> fetchFields)
{
var fields = $"new ({string.Join(",", fetchFields)})";
var res = list.AsQueryable().Select(fields);
//For test only to check the value of selected fields
foreach (dynamic item in res) {
Console.WriteLine(item.id_state);
Console.WriteLine(item.id_country);
}
}
OUTPUT
1
IND
2
IND
3
IND
4
IND
EXPLANATION
I think the difference is that specifying explicitly the type (through generic T or through RateInfo) you force LINQ to know list items'type; if you use dynamic the IQueryable.ElementType of the IQuqryable instance has value System.Object, so the query fails with the error you've experienced.

You should try using generics:
private void GetDynamicData<T>(IEnumerable<T> list, List<string> fetchFields)
{
var data = list.AsQueryable();

How do I flatten an array of arrays?

I have an array consisting of following elements:
var schools = new [] {
new object[]{ new[]{ "1","2" }, "3","4" },
new object[]{ new[]{ "5","6" }, "7","8" },
new object[]{ new[]{ "9","10","11" }, "12","13" }
};
The real object that i try to flatten is from importing data into array of arrays from CSV and then joining it on values of fields:
var q =
from c in list
join p in vocatives on c.Line[name1].ToUpper() equals p.first_name.ToUpper() into ps
from p in ps.DefaultIfEmpty()
select new object[] { c.Line, p == null ? "(No vocative)" : p.vocative, p == null ? "(No sex)" : p.sex };
I want to flatten that array of strings to get:
string[] {
new string[]{ "1","2","3","4" },
new string[]{ "5","6","7","8" },
new string[]{ "9","10","11","12","13" }
}
I already have an solution that does that in loop, its not so performance-wise, but it seems to work ok.
I've tried to use SelectMany but cannot make up a solution.
Thank you very much for feedback ;)
I've tried answer from npo:
var result = schools.Select(z => z.SelectMany(y=> y.GetType().IsArray
? (object[])y : new object[] { y })
);
But CSVwriter class method accepts only explicitly typed:
IEnumerable<string[]>
So how to do it in linq, I've tried to:
List<string[]> listOflists = (List<string[]>)result;
But no go, InvalidCastException arrises, unfortunately.

In a first step, you have to normalize the data to one kind of type. Then you can iterate over them as you like. So at first create a method to flatten the values from a specific point to an arbitrary depth:
public static class Extensions
{
public static IEnumerable<object> FlattenArrays(this IEnumerable source)
{
foreach (var item in source)
{
if (item is IEnumerable inner
&& !(item is string))
{
foreach (var innerItem in inner.FlattenArrays())
{
yield return innerItem;
}
}
yield return item;
}
}
}
Now you can either iterate on the top level to get a single array of all values:
// Produces one array => ["1", "2", "3", "4", ...]
var allFlat = schools.FlattenArrays().OfType<string>().ToArray();
Or you can create individual array one depth deeper:
foreach (var item in schools)
{
// Produces an array for each top level e.g. ["5", "6", "7", "8"]
var flat = item.FlattenArrays().OfType<string>().ToArray();
}

As per the comments, because your inner array mixes elements of string[] and string, it likely won't be trivial to do this directly in Linq.
However, with the assistance of a helper function (I've called Flattener) you can branch the handling of both of the inner types manually to either return the elements in the array (if it's string[]), or to return the single element as an enumerable, if it's not. SelectMany can then be used to flatten the inner level, but the outer level seemingly you want to leave unflattened:
i.e.
var schools = new [] {
new object[]{new[]{"1","2"}, "3","4"},
new object[]{new[]{"5","6"}, "7","8"},
new object[]{new[]{"9","10","11"}, "12","13"}
};
var result = schools
.Select(s => s.SelectMany(o => Flattener(o)));
Which returns a type of IEnumerable<IEnumerable<string>>
Where the messy unpacking bit done by:
public IEnumerable<string> Flattener(object o)
{
if (o is IEnumerable<string> strings)
{
return strings;
}
if (o is string s)
{
return new[]{s};
}
return new[]{"?"};
}
Note the above uses the pattern matching capabilities of C#7.
Result screenshot courtesy of LinqPad:

If you want o do it via linq here is a sample
var schools = new[] {
new object[]{new[]{"1","2"}, "3","4"},
new object[]{new[]{"5","6"}, "7","8"},
new object[]{new[]{"9","10","11"}, "12","13"}
};
var result = schools.Select(z => z.SelectMany(y=> y.GetType().IsArray ? (object[])y : new object[] { y }));

The presented solution is devoted to convert any sort of int array, regular, jagged, or nested (these last are taken from javascript and its object notation, but they can also be implemented as complex jagged array of objects in C#), into a simple mono-dimensional integers array.
To adapt your request to it, you should have only change the string type elements of your objects jagged array into int type.
Here it is the C# function:
public static int[] getFlattenedIntArray(object jaggedArray)
{
var flattenedArray = new List<int>();
var jaggedArrayType = jaggedArray.GetType();
var expectedType = typeof(int);
if (jaggedArrayType.IsArray)
{
if (expectedType.IsAssignableFrom(jaggedArrayType.GetElementType()))
{
foreach (var el in jaggedArray as int[])
{
flattenedArray.Add(el);
}
}
else
{
foreach (var el in jaggedArray as object[])
{
foreach (var retIntEl in getFlattenedIntArray(el))
{
flattenedArray.Add(retIntEl);
}
}
}
}
else if (jaggedArrayType == expectedType)
{
flattenedArray.Add((int)jaggedArray);
}
else
{
return new int[0];
}
return flattenedArray.ToArray();
}
Try it in this fiddle: https://dotnetfiddle.net/5HGX96

A VFP-Cursor in C#?

I'm having a old Visual FoxPro programm, which i need to rewrite in c#.
There we used the cursors from VFP, to read .txt-files and load it into temporary cursors.
Looks for example like this in FoxPro: (mb5b is the mb5b-textfile)
SELECT werk,matnr,ALLTRIM(matnr)+ALLTRIM(werk) as matwerk,sum(zugang) as zugang,sum(abgang) as abgang INTO CURSOR mb5b_temp FROM mb5b GROUP BY werk,matnr
Those cursors dont exist in c#. (I didnt found anything like this.)
So im creating a DataTable and while reading the file I insert it into the DataTable.
DataTable dt_mb5b_temp = new DataTable();
dt_mb5b_temp.Columns.Add("matnr");
dt_mb5b_temp.Columns.Add("werk");
dt_mb5b_temp.Columns.Add("matwerk");
dt_mb5b_temp.Columns.Add("zugang");
dt_mb5b_temp.Columns.Add("abgang");
while ((mb5bline = sr_mb5b.ReadLine()) != null)
{
DataRow dr = dt_mb5b_temp.NewRow();
string[] mb5b = mb5bline.Split(new Char[] { '|' });
dr["matnr"] = mb5b[1].Trim();
dr["werk"] = mb5b[2].Trim();
dr["matwerk"] = mb5b[1].Trim() + mb5b[2].Trim();
dr["zugang"] = mb5b[6].Trim();
dr["abgang"] = mb5b[7].Trim();
}
I thought i may can work with the DataTable.Select() to use a select-statment as above, but it doesnt work ... And other solutions dont come to my mind at the moment :/
For sure i could also insert it into a DB - then use select, but i try to avoid this (Would need two extra tables, and i think those inserts and select will take a long time).
Is there any possibility to get this working ?
Thanks!
If you need anymore Informations, please tell.

look at this site. http://www.dotnetperls.com/readline
using System;
using System.Collections.Generic;
using System.IO;
class Program
{
static void Main()
{
const string f = "TextFile1.txt";
// 1
// Declare new List.
List<string> lines = new List<string>();
// 2
// Use using StreamReader for disposing.
using (StreamReader r = new StreamReader(f))
{
// 3
// Use while != null pattern for loop
string line;
while ((line = r.ReadLine()) != null)
{
// 4
// Insert logic here.
// ...
// "line" is a line in the file. Add it to our List.
lines.Add(line);
}
}
// 5
// Print out all the lines.
foreach (string s in lines)
{
Console.WriteLine(s);
}
}
}
Output
(Prints contents of TextFile1.txt)
This is a text file I created,
Just for this article.
group by ienum
class Pet
{
public string Name { get; set; }
public int Age { get; set; }
}
// Uses method-based query syntax.
public static void GroupByEx1()
{
// Create a list of pets.
List<Pet> pets =
new List<Pet>{ new Pet { Name="Barley", Age=8 },
new Pet { Name="Boots", Age=4 },
new Pet { Name="Whiskers", Age=1 },
new Pet { Name="Daisy", Age=4 } };
// Group the pets using Age as the key value
// and selecting only the pet's Name for each value.
IEnumerable<IGrouping<int, string>> query =
pets.GroupBy(pet => pet.Age, pet => pet.Name);
// Iterate over each IGrouping in the collection.
foreach (IGrouping<int, string> petGroup in query)
{
// Print the key value of the IGrouping.
Console.WriteLine(petGroup.Key);
// Iterate over each value in the
// IGrouping and print the value.
foreach (string name in petGroup)
Console.WriteLine(" {0}", name);
}
}
/*
This code produces the following output:
8
Barley
4
Boots
Daisy
1
Whiskers
*/

c# Intersection and Union not working correctly

I am using C# 4.0 in VS 2010 and trying to produce either an intersection or a union of n sets of objects.
The following works correctly:
IEnumerable<String> t1 = new List<string>() { "one", "two", "three" };
IEnumerable<String> t2 = new List<string>() { "three", "four", "five" };
List<String> tInt = t1.Intersect(t2).ToList<String>();
List<String> tUnion = t1.Union(t2).ToList<String>();
// this also works
t1 = t1.Union(t2);
// as does this (but not at the same time!)
t1 = t1.Intersect(t2);
However, the following doesn't. These are code snippets.
My class is:
public class ICD10
{
public string ICD10Code { get; set; }
public string ICD10CodeSearchTitle { get; set; }
}
In the following:
IEnumerable<ICD10Codes> codes = Enumerable.Empty<ICD10Codes>();
IEnumerable<ICD10Codes> codesTemp;
List<List<String>> terms;
// I create terms here ----
// and then ...
foreach (List<string> item in terms)
{
// the following line produces the correct results
codesTemp = dataContextCommonCodes.ICD10Codes.Where(e => item.Any(k => e.ICD10CodeSearchTitle.Contains(k)));
if (codes.Count() == 0)
{
codes = codesTemp;
}
else if (intersectionRequired)
{
codes = codes.Intersect(codesTemp, new ICD10Comparer());
}
else
{
codes = codes.Union(codesTemp, new ICD10Comparer());
}
}
return codes;
The above only ever returns the results of the last item searched.
I also added my own comparer just in case, but this made no difference:
public class ICD10Comparer : IEqualityComparer<ICD10Codes>
{
public bool Equals(ICD10Codes Code1, ICD10Codes Code2)
{
if (Code1.ICD10Code == Code2.ICD10Code) { return true; }
return false;
}
public int GetHashCode(ICD10Codes Code1)
{
return Code1.ICD10Code.GetHashCode();
}
}
I am certain I am overlooking something obvious - I just cannot see what it is!

This code: return codes; returns a deferred enumerable. None of the queries have been executed to fill the set. Some queries get executed each time through the loop to make a Count though.
This deferred execution is a problem because of the closure issue... at the return, item is bound to the last loop execution.
Resolve this by forcing the queries to execute in each loop execution:
if (codes.Count() == 0)
{
codes = codesTemp.ToList();
}
else if (intersectionRequired)
{
codes = codes.Intersect(codesTemp, new ICD10Comparer()).ToList();
}
else
{
codes = codes.Union(codesTemp, new ICD10Comparer()).ToList();
}

if you are using an own comparer, you should take a look at the correct implementation of the GetHashCode function. the linq operators use this comparison too. you can take a look here:
http://msdn.microsoft.com/en-us/library/system.object.gethashcode(v=vs.80).aspx
you could try changing the hash function to "return 0", to see if it is the problem. ICD10Code.GetHashCode will return perhaps different values if it is a class object

Your problem definitely is not connect to Intersect or Union LINQ extension methods. I've just tested following:
var t1 = new List<ICD10>()
{
new ICD10() { ICD10Code = "123" },
new ICD10() { ICD10Code = "234" },
new ICD10() { ICD10Code = "345" }
};
var t2 = new List<ICD10>()
{
new ICD10() { ICD10Code = "234" },
new ICD10() { ICD10Code = "456" }
};
// returns list with just one element - the one with ICF10Code == "234"
var results = t1.Intersect(t2, new ICD10Comparer()).ToList();
// return list with 4 elements
var results2 = t1.Union(t2, new ICD10Comparer()).ToList();
Using your ICD10 and ICD10Comparer classes declarations. Everything works just fine! You have to search for bug in your custom code, because LINQ works just fine.

Creating a two-dimensional array

I am trying to create a two dimensional array and I am getting so confused. I was told by a coworker that I need to create a dictionary within a dictionary for the array list but he couldn't stick around to help me.
I have been able to create the first array that lists the the programs like this
+ project 1
+ project 2
+ project 3
+ project 4
The code that accomplishes this task is below-
var PGList = from x in db.month_mapping
where x.PG_SUB_PROGRAM == SP
select x;
//select x.PG.Distinct().ToArray();
var PGRow = PGList.Select(x => new { x.PG }).Distinct().ToArray();
So that takes care of my vertical array and now I need to add my horizontal array so that I can see the total amount spent in each accounting period. So the final output would look like this but without the dashes of course.
+ program 1-------100---200---300---400---500---600---700---800---900---1000---1100---1200
+ program 2-------100---200---300---400---500---600---700---800---900---1000---1100---1200
+ program 3-------100---200---300---400---500---600---700---800---900---1000---1100---1200
+ program 4-------100---200---300---400---500---600---700---800---900---1000---1100---1200
I have tried to use a foreach to cycle through the accounting periods but it doesn't work. I think I might be on the right track and I was hoping SO could provide some guidance or at the very least a tutorial for me to follow. I have posted the code that I written so far on the second array below. I am using C# and MVC 3. You might notice that their is no dictionary within a dictionary. If my coworker is correct how would I do something like that, I took a look at this question using dictionary as a key in other dictionary but I don't understand how I would use it in this situation.
Dictionary<string, double[]> MonthRow = new Dictionary<string, double[]>();
double[] PGContent = new double[12];
string lastPG = null;
foreach (var item in PGRow)
{
if (lastPG != item.PG)
{
PGContent = new double[12];
}
var MonthList = from x in db.Month_Web
where x.PG == PG
group x by new { x.ACCOUNTING_PERIOD, x.PG, x.Amount } into pggroup
select new { accounting_period = pggroup.Key.ACCOUNTING_PERIOD, amount = pggroup.Sum(x => x.Amount) };
foreach (var P in MonthList)
{
int accounting_period = int.Parse(P.accounting_period) - 1;
PAContent[accounting_period] = (double)P.amount;
MonthRow[item.PG] = PGContent;
lastPG = item.PG;
}
I hope I have clearly explained my issue, please feel free to ask for any clarification needed as I need to solve this problem and will be checking back often. Thanks for your help!

hope this helps.
// sample data
var data = new Dictionary<string, List<int>>();
data.Add("program-1", new List<int>() { 100, 110, 130 });
data.Add("program-2", new List<int>() { 200, 210, 230 });
data.Add("brogram-3", new List<int>() { 300, 310, 330 });
// query data
var newData = (from x in data
where x.Key.Contains("pro")
select x).ToDictionary(v => v.Key, v=>v.Value);
// display selected data
foreach (var kv in newData)
{
Console.Write(kv.Key);
foreach (var val in kv.Value)
{
Console.Write(" ");
Console.Write(val.ToString());
}
Console.WriteLine();
}
output is:
program-1 100 110 130
program-2 200 210 230

Don't try to use anonymous types or LINQ projection to create new data types, especially if you're a beginner, you will just get confused. If you want a specialized data type, define one; e.g.:
public class Account
{
public string Name { get; private set; }
public decimal[] MonthAmount { get; private set; }
readonly int maxMonths = 12;
public Account(string name, ICollection<decimal> monthAmounts)
{
if (name == null)
throw new ArgumentNullException("name");
if (monthAmounts == null)
throw new ArgumentNullException("monthAmounts");
if (monthAmounts.Count > maxMonths)
throw new ArgumentOutOfRangeException(string.Format(" monthAmounts must be <= {0}", maxMonths));
this.Name = name;
this.MonthAmount = new decimal[maxMonths];
int i = 0;
foreach (decimal d in monthAmounts)
{
this.MonthAmount[i] = d;
i++;
}
}
}
Use instances of this type directly, you do not have to convert them to arrays, dictionaries, lists, or anything else:
var accountPeriods = new List<Account>();
accountPeriods.Add(new Account("program-1", new decimal[] { 1, 2, 3, 4 }));
You can use LINQ or whatever to query or alter instances of your new type:
foreach (Account a in accountPeriods)
foreach (decimal d in a.MonthAmount)
DoSomethingWith(d);
That should be enough to get you started.

I want to thank #Ray Cheng and #Dour High Arch for their help but I have figured out another way to accomplish this task and I wanted to post my code so that the next person that is having the same trouble can figure out their problem faster.
Above I split my code into more managable sections to explain my problem as clearly as I could and the code below has all those parts combined so you can see the big picture. This code returns an array that contains the program and the amounts for every month.
public virtual ActionResult getAjaxPGs(string SP = null)
{
if (SP != null)
{
var PGList = from x in db.month_mapping
where x.PG_SUB_PROGRAM == SP
select x;
var PGRow = PGList.Select(x => new { x.PG }).Distinct().ToArray();
float[] PGContent = new float[12];
Dictionary<string,float[]> MonthRow = new Dictionary<string, float[]>();
foreach (var item in PGRow)
{
PGContent = new float[12];
var MonthList = from x in db.month_Web
where x.PG == item.PG
group x by new { x.ACCOUNTING_PERIOD, x.PG, x.Amount } into pggroup
select new { accounting_period = pggroup.Key.ACCOUNTING_PERIOD, amount = pggroup.Sum(x => x.Amount) };
foreach (var mon in MonthList)
{
int accounting_period = int.Parse(mon.accounting_period) - 1;
PGContent[accounting_period] = (float)mon.amount/1000000;
}
MonthRow[item.PG] = PGContent;
}
return Json(MonthRow, JsonRequestBehavior.AllowGet);
}
return View();
}
This code worked great for me since I am pulling from a Linq to SQL query instead of adding data directly into the code. My problems stemmed from mainly putting the data pulls outside of the foreach loops so it only pulled 1 piece of data from the SQL instead of all twelve months. I hope this helps some one else who is trying to pull data in from SQL data sources into multidimensional arrays.