When i comment dishes.Add(new Dishes { DishID = 8, DishName = "Name", DishTypeID = 2, IngredientID = 2 }); i get in ll one item Amount="1 cup" DishID=1 Ingridient="egg" Name ="Soup". When uncomment that line raising error, null reference exception in b.IngredientTypeID. The main question how to get in ll two item's:
1) Amount="1 cup" DishID=1 Ingridient="egg" Name ="Soup"
2) Amount=null DishID=2 Ingridient=null Name =null
namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
List<Dishes> dishes = new List<Dishes>();
List<Ingredients> ingredients = new List<Ingredients>();
List<Amount> amount = new List<Amount>();
List<Ingredient> ingredient = new List<Ingredient>();
dishes.Add(new Dishes { DishID = 1, DishName = "Soup", DishTypeID = 1, IngredientID = 1 });
//dishes.Add(new Dishes { DishID = 8, DishName = "Name", DishTypeID = 2, IngredientID = 2 });
ingredients.Add(new Ingredients { AmountID = 2, IngredientID = 1, IngredientTypeID = 1, IngredientUniqID = 1 });
amount.Add(new Amount { AmountID = 2, AmountName = "1 cup" });
ingredient.Add(new Ingredient { IngredientID = 1, IngredientName = "egg" });
var test = from dish in dishes
join ing in ingredients on dish.IngredientID equals ing.IngredientID into result
from b in result.DefaultIfEmpty()
join i in ingredient on b.IngredientTypeID equals i.IngredientID into r
from c in r.DefaultIfEmpty()
join am in amount on b.AmountID equals am.AmountID into s
from t in s.DefaultIfEmpty()
select new DisplayRecipe { Name = dish.DishName, Amount = t.AmountName, Ingredient = c.IngredientName, DishID = dish.DishID };
List<DisplayRecipe> ll = test.ToList();
}
}
public partial class Dishes
{
public int DishID { get; set; }
public string DishName { get; set; }
public Nullable<int> DishTypeID { get; set; }
public Nullable<int> IngredientID { get; set; }
}
public partial class Ingredients
{
public int IngredientID { get; set; }
public Nullable<int> AmountID { get; set; }
public Nullable<int> IngredientTypeID { get; set; }
public int IngredientUniqID { get; set; }
}
public partial class Amount
{
public int AmountID { get; set; }
public string AmountName { get; set; }
}
public partial class Ingredient
{
public int IngredientID { get; set; }
public string IngredientName { get; set; }
}
public class DisplayRecipe
{
public string Name { get; set; }
public string Ingredient { get; set; }
public string Amount { get; set; }
public int DishID { get; set; }
}
}
The problem is that any of the b, c, t variables can be null due to DefaultIfEmpty and you need to account for that in any member access, including join conditions.
If you are using C#6 (VS2015), you can use ?. operator like this
var test = from dish in dishes
join ing in ingredients on dish.IngredientID equals ing.IngredientID into result
from b in result.DefaultIfEmpty()
join i in ingredient on b?.IngredientTypeID equals i.IngredientID into r
from c in r.DefaultIfEmpty()
join am in amount on b?.AmountID equals am.AmountID into s
from t in s.DefaultIfEmpty()
select new DisplayRecipe { Name = dish.DishName, Amount = t?.AmountName, Ingredient = c?.IngredientName, DishID = dish.DishID };
while in pre C#6:
var test = from dish in dishes
join ing in ingredients on dish.IngredientID equals ing.IngredientID into result
from b in result.DefaultIfEmpty()
join i in ingredient on b != null ? b.IngredientTypeID : null equals i.IngredientID into r
from c in r.DefaultIfEmpty()
join am in amount on b != null ? b.AmountID : null equals am.AmountID into s
from t in s.DefaultIfEmpty()
select new DisplayRecipe { Name = dish.DishName, Amount = t != null ? t.AmountName : null, Ingredient = c != null ? c.IngredientName : null, DishID = dish.DishID };
Problem is you added this line:
dishes.Add(new Dishes { DishID = 8, DishName = "Name", DishTypeID = 2, IngredientID = 2 });
But did not also add the other lines that are dependent on your join (example):
ingredients.Add(new Ingredients { AmountID = 2, IngredientID = 2, IngredientTypeID = 1, IngredientUniqID = 1 });
ingredient.Add(new Ingredient { IngredientID = 2, IngredientName = "ham" });
So when your program tries to find an ingredientID of 2 because that has been added to dishes it does not find one and produces an error.
Sample of code that works:
dishes.Add(new Dishes { DishID = 1, DishName = "Soup", DishTypeID = 1, IngredientID = 1 });
dishes.Add(new Dishes { DishID = 8, DishName = "Name", DishTypeID = 2, IngredientID = 2 });
ingredients.Add(new Ingredients { AmountID = 2, IngredientID = 1, IngredientTypeID = 1, IngredientUniqID = 1 });
ingredients.Add(new Ingredients { AmountID = 2, IngredientID = 2, IngredientTypeID = 1, IngredientUniqID = 1 });
amount.Add(new Amount { AmountID = 2, AmountName = "1 cup" });
ingredient.Add(new Ingredient { IngredientID = 1, IngredientName = "egg" });
ingredient.Add(new Ingredient { IngredientID = 2, IngredientName = "ham" });
Related
Sorry for my bad English.
Here is my SQL Design.
I have 3 table in Sqlsever. Each table has 4 column with same name, same datatype.
And i want to get data from 4 column "Id, Name, Quantity, IdCategory" from 3 table into 1 list object same as returning value in this code below:
public async Task<IEnumerable<Shirt>> LoadAllShirt()
{
return await _dbContext.Shirt.ToListAsync();
}
I use .NET Core 6 Mvc - code first. Thanks for your help.
I have 3 table in Sqlsever. Each table has 4 column with same name,
same datatype. And I want to get data from 4 column "Id, Name,
Quantity, IdCategory" from 3 table into 1 list, I use .NET Core 6 Mvc - code first.
Well, lot of way around to handle this kind of scenario. Most easy and convenient way I would prefer to use View model or using Linq query.
Lets assume you have below Models:
Models:
public class Bags
{
public int Id { get; set; }
public string Name { get; set; }
public int Quantity { get; set; }
public string Category { get; set; }
}
public class Shirts
{
public int Id { get; set; }
public string Name { get; set; }
public int Quantity { get; set; }
public string Category { get; set; }
}
public class Shoes
{
public int Id { get; set; }
public string Name { get; set; }
public int Quantity { get; set; }
public string Category { get; set; }
}
Seeds In Models:
List<Bags> listBags = new List<Bags>();
listBags.Add(new Bags() { Id = 101, Name = "Bag A", Quantity =10, Category = "Cat-A"});
listBags.Add(new Bags() { Id = 102, Name = "Bag B", Quantity =15, Category = "Cat-A"});
listBags.Add(new Bags() { Id = 103, Name = "Bag C", Quantity =20, Category = "Cat-A"});
List<Shirts> listShirts = new List<Shirts>();
listShirts.Add(new Shirts() { Id = 101, Name = "Shirt A", Quantity = 10, Category = "Cat-B" });
listShirts.Add(new Shirts() { Id = 102, Name = "Shirt B", Quantity = 15, Category = "Cat-B" });
listShirts.Add(new Shirts() { Id = 103, Name = "Shirt C", Quantity = 20, Category = "Cat-B" });
List<Shoes> listShoes = new List<Shoes>();
listShoes.Add(new Shoes() { Id = 101, Name = "Shirt A", Quantity = 10, Category = "Cat-S" });
listShoes.Add(new Shoes() { Id = 102, Name = "Shirt B", Quantity = 15, Category = "Cat-S" });
listShoes.Add(new Shoes() { Id = 103, Name = "Shirt C", Quantity = 20, Category = "Cat-S" });
Way: 1 using ViewModel:
public class AllViewModel
{
public List<Bags> Bags { get; set; }
public List<Shirts> Shirts { get; set; }
public List<Shoes> Shoes { get; set; }
}
Query Using ViewModel:
var allTableUsingViewModel = new AllViewModel();
allTableUsingViewModel.Bags = listBags;
allTableUsingViewModel.Shirts = listShirts;
allTableUsingViewModel.Shoes = listShoes;
Output Using ViewModel:
Way: 2 using Linq Annonymous Type:
Query Using Linq Annonymous Type:
var AllTableListUsingLinq = from a in listBags
join b in listShirts on a.Id equals b.Id
join c in listShoes on b.Id equals c.Id
select new
{
FromBagsID = a.Id,
FromBagsName = a.Name,
FromBagsQuantity = a.Quantity,
FromBagsCategory = a.Category,
FromShirtsID = b.Id,
FromShirtsName = b.Name,
FromShirtsQuantity = b.Quantity,
FromShirtsCategory = b.Category,
FromShoesID = c.Id,
FromShoesName = c.Name,
FromShoesQuantity = c.Quantity,
FromShoesCategory = c.Category
};
Output Using Linq Annonymous Type:
Full Controller:
[HttpGet("GetFrom3Tables")]
public IActionResult GetFrom3Tables()
{
List<Bags> listBags = new List<Bags>();
listBags.Add(new Bags() { Id = 101, Name = "Bag A", Quantity =10, Category = "Cat-A"});
listBags.Add(new Bags() { Id = 102, Name = "Bag B", Quantity =15, Category = "Cat-A"});
listBags.Add(new Bags() { Id = 103, Name = "Bag C", Quantity =20, Category = "Cat-A"});
List<Shirts> listShirts = new List<Shirts>();
listShirts.Add(new Shirts() { Id = 101, Name = "Shirt A", Quantity = 10, Category = "Cat-B" });
listShirts.Add(new Shirts() { Id = 102, Name = "Shirt B", Quantity = 15, Category = "Cat-B" });
listShirts.Add(new Shirts() { Id = 103, Name = "Shirt C", Quantity = 20, Category = "Cat-B" });
List<Shoes> listShoes = new List<Shoes>();
listShoes.Add(new Shoes() { Id = 101, Name = "Shirt A", Quantity = 10, Category = "Cat-S" });
listShoes.Add(new Shoes() { Id = 102, Name = "Shirt B", Quantity = 15, Category = "Cat-S" });
listShoes.Add(new Shoes() { Id = 103, Name = "Shirt C", Quantity = 20, Category = "Cat-S" });
//Way: 1 Linq Query
var AllTableListUsingLinq = from a in listBags
join b in listShirts on a.Id equals b.Id
join c in listShoes on b.Id equals c.Id
select new
{
FromBagsID = a.Id,
FromBagsName = a.Name,
FromBagsQuantity = a.Quantity,
FromBagsCategory = a.Category,
FromShirtsID = b.Id,
FromShirtsName = b.Name,
FromShirtsQuantity = b.Quantity,
FromShirtsCategory = b.Category,
FromShoesID = c.Id,
FromShoesName = c.Name,
FromShoesQuantity = c.Quantity,
FromShoesCategory = c.Category
};
//Way: 2 : ViewModel
var allTableUsingViewModel = new AllViewModel();
allTableUsingViewModel.Bags = listBags;
allTableUsingViewModel.Shirts = listShirts;
allTableUsingViewModel.Shoes = listShoes;
return Ok(AllTableListUsingLinq);
}
Note: If you need more information you could check our official document for View Model and Linq Projction here
The following sample query will list your 3 types of data into a single result set.
var allResults = resultSet1.Concat(resultSet2);
For the return type create a class which will be the parent class for all your products (Bag,Shirt,Shoes) Which will help you to return data in a single Generic data.
If you use any non-generic list to send the data like hashtable or Arraylist then then there will be no issue.
In my way I will suggest to use generic data list as it will help you fetch data in better time complexity.
In this case you may need to define additional indirect base class with these 4 parameters. Than you can create Collection of this base class, and concatinate all 3 tables into.
public class BaseEntity
{
public string Name {get;set;}
}
public class Shoes : BaseEntity
{
}
...
public IEnumerable<BaseEntity> GetAllTables()
{
var shirts = await _dbContext.Shirt.ToListAsync();
var shoes = await _dbContext.Shoes.ToListAsync();
var bags = await _dbContext.Bags.ToListAsync();
return shirts.Concat(shoes).Concat(bags);
}
Similar example but witout casting to base class is shown in Enumerable.Concat documentation: https://learn.microsoft.com/pl-pl/dotnet/api/system.linq.enumerable.concat?view=net-7.0
There is three table:
Brand Category
----------------------- --------------------------------
BrandID BrandName CategoryID CategoryName
----------------------- --------------------------------
1 Brand1 1 cat1
2 Brand2 2 cat2
Product
------------------------------------------------------------
ProductID BrandID CategoryID ProductName
------------------------------------------------------------
1 1 1 Product1
2 1 1 Product2
3 1 2 Product3
4 2 1 Product4
I want to write Llinq query to get output like below:
Brand1
|__ cat1
| |__ Product1
| |__ Product2
|
|__ Cat2
| |__ Product3
|
|__ Brand2
|__ cat1
| |__ Product4
I Wrote this query to get Product group by Category:
var query2 = db.Brands
.GroupBy(x => new { x.BrandID, x.BrandName })
.Select(x => new
{
x.Key.BrandID,
x.Key.BrandName,
ProductsNames = db.Products
.Where(p => p.BrandID == x.Key.BrandID)
.Select(p => p.ProductName).ToList()
}).ToList();
How can Group Products by Brand then by Category?
You can do this in 2 steps
//Step 1 - Join 3 lists
var query = (from p in products
join b in brands on p.BrandId equals b.Id
join c in categories on p.CategoryId equals c.Id
select new
{
b.BrandName,
c.CategoryName,
p.ProductName
}).ToList();
//Step 2 - query required results
var results = query
.GroupBy(x => new { x.BrandName, x.CategoryName })
.Select(x => new
{
Brand = x.Key.BrandName,
Category = x.Key.CategoryName,
Product = x.Select(y=>y.ProductName).ToList()
});
Console.WriteLine(JsonConvert.SerializeObject(results));
OUTPUT
[
{
"Brand": "Brand1",
"Category": "cat1",
"Product": [
"Product1",
"Product2"
]
},
{
"Brand": "Brand1",
"Category": "cat2",
"Product": [
"Product3"
]
},
{
"Brand": "Brand2",
"Category": "cat1",
"Product": [
"Product4"
]
}
]
I wrote a little console program:
class Program
{
static void Main(string[] args)
{
var products = new List<Product>{
new Product { ProductID = 1, BrandID = 1, CategoryID = 1, ProductName = "Product1" },
new Product { ProductID = 2, BrandID = 1, CategoryID = 1, ProductName = "Product2" },
new Product { ProductID = 3, BrandID = 1, CategoryID = 2, ProductName = "Product3" },
new Product { ProductID = 4, BrandID = 2, CategoryID = 1, ProductName = "Product4" }
};
var groupedByBrand =
products
.GroupBy(p => p.BrandID)
.Select(g => g.GroupBy(p => p.CategoryID));
foreach (var groupByBrand in groupedByBrand)
foreach (var groupByCategory in groupByBrand)
foreach (var product in groupByCategory)
Console.WriteLine($"{product.BrandID} - {product.ProductName}");
}
}
public class Product
{
public int ProductID { get; internal set; }
public int BrandID { get; internal set; }
public int CategoryID { get; internal set; }
public string ProductName { get; internal set; }
}
I grouped by BrandId and then inside this group grouped by categoryId.
If it is just about the grouping you can use the BrandID and CategoryID and don't even need to join the tables. if you want to sort by name then of course you need to join.
Maybe you wanted to do some sorting on top of / instead of grouping?
In one step , more compact manner
public class Product
{
public int ProductID { get; internal set; }
public string ProductName { get; internal set; }
public Brand brand { get; set; }
public Category cat { get; set; }
public Product()
{
brand = new Brand();
cat = new Category();
}
}
public class Brand
{
public int BrandID { get; internal set; }
public string BrandName { get; internal set; }
}
public class Category
{
public int CategoryID { get; internal set; }
public string CategoryName { get; internal set; }
}
private void a1()
{
var products = new List<Product>{
new Product { ProductID = 1,
brand =new Brand { BrandID = 1, BrandName = "Brand1" },
cat = new Category { CategoryID = 1, CategoryName = "cat1" },
ProductName = "Product1" },
new Product { ProductID = 2,
brand =new Brand { BrandID = 1, BrandName = "Brand1" },
cat = new Category { CategoryID = 1, CategoryName = "cat1" },
ProductName = "Product2" },
new Product { ProductID = 3,
brand =new Brand { BrandID = 1, BrandName = "Brand1" },
cat = new Category { CategoryID = 2, CategoryName = "cat2" },
ProductName = "Product3" },
new Product { ProductID = 4,
brand =new Brand { BrandID = 2, BrandName = "Brand2" },
cat = new Category { CategoryID = 1, CategoryName = "cat1" },
ProductName = "Product4" }
};
var g1 = products.GroupBy(p => new { p.brand, p.cat, p })
.Select(y => new
{
k1 = y.Key.brand.BrandName,
k2 = y.Key.cat.CategoryName,
k3 = y.Key.p.ProductName
}
);
}
// Result/Output as below
{ k1 = "Brand1", k2 = "cat1", k3 = "Product1" }
{ k1 = "Brand1", k2 = "cat1", k3 = "Product2" }
{ k1 = "Brand1", k2 = "cat2", k3 = "Product3" }
{ k1 = "Brand2", k2 = "cat1", k3 = "Product4" }
I have retrieve a list of employees. my employee class columns(employeeId, lastname, genderid)
List<m_employees> Items = new List<m_employees>
{
new m_employees{ employeeid = 1, lastname = "mike", genderid = 1 },
new m_employees{ employeeid = 2, lastname = "jeni", genderid = 2 }
};
then i have my gender class columns (id, title)
List<m_genders> genders = new List<m_genders>
{
new m_genders{ id = 1, title = "Male" },
new m_genders{ id = 2, title = "Female" }
};
//then i tried joining the retrieved list of employees to the genders
var x = from emp in Items
join sex in genders
on emp.genderid equals sex.id
into a from b in a.DefaultIfEmpty(new m_genders())
select new
{
emp.lastname,
emp.genderid,
sex = b.title
};
red error line is showing to the keyword join and says "the type of one of the expressions in the join clause is incorrect..."
how can i join them properly?
This happens because types emp.genderid, sex.id are different and you need to cast or convert them explicitly like that:
(int)emp.genderid equals sex.id
I was able to reproduce the error with the following class definition:
class m_genders
{
public int id { get; set; }
public string title { get; set; }
}
class employee
{
public int id;
public uint genderid;
public string lastname { get; set; }
}
Your question is not clear, the code work without any problem :
namespace WindowsFormsApp1
{
public class m_genders
{
public int id;
public string title;
}
public class m_employees
{
public int employeeid { get; set; }
public int genderid { get; set; }
public string lastname { get; set; }
}
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void button1_Click(object sender, EventArgs e)
{
List<m_genders> genders = new List<m_genders>
{
new m_genders {id = 1, title = "Male"},
new m_genders {id = 2, title = "Female"}
};
List<m_employees> Items = new List<m_employees>
{
new m_employees{ employeeid = 1, lastname = "mike", genderid = 1 },
new m_employees{ employeeid = 2, lastname = "jeni", genderid = 2 }
};
var x = from emp in Items
join sex in genders
on emp.genderid equals sex.id
into a
from b in a.DefaultIfEmpty(new m_genders())
select new
{
emp.lastname,
emp.genderid,
sex = b.title
};
}
}
}
I have created 2 models to store the results of an sql query. Now I would like to join them for each of the week's... (week1 = Record_id, week2 = Record_id)
to get a new Object in which I would have all the data from the 1st model, as well as map data from the "Category" Model to it.
I created a new Model for it, but I am not sure how to write a linq query
First Model:
public class CustomData
{
public string full_name { get; set; }
public string location { get; set; }
public int week1 { get; set; }
public int week2 { get; set; }
public int week3 { get; set; }
}
Second Model:
public class Category
{
public int Record_ID { get; set; }
public int Color{ get; set; }
public string Name { get; set; }
}
New Model for end result:
public class WeekView
{
public string full_name { get; set; }
public string location { get; set; }
public Category week1 { get; set; }
public Category week2 { get; set; }
public Category week3 { get; set; }
}
This should work:
List<CustomData> list = new List<CustomData>();
list.Add(new CustomData() { full_name = "test", location = "test", week1 = 0, week2 = 1, week3 = 2 });
list.Add(new CustomData() { full_name = "test2", location = "test2", week1 = 0, week2 = 12, week3 = 22 });
List<Category> categories = new List<Category>();
categories.Add(new Category { Color = 0, Name = "testName", Record_ID = 0 });
categories.Add(new Category { Color = 1, Name = "testName1", Record_ID = 1 });
categories.Add(new Category { Color = 2, Name = "testName2", Record_ID = 2 });
categories.Add(new Category { Color = 3, Name = "testName3", Record_ID = 12 });
categories.Add(new Category { Color = 4, Name = "testName4", Record_ID = 22 });
List<WeekView> results = new List<WeekView>();
results.AddRange(list.Select(x=>
new WeekView() { full_name = x.full_name,
location = x.location,
week1 = categories.FirstOrDefault(c => c.Record_ID == x.week1),
week2 = categories.FirstOrDefault(c => c.Record_ID == x.week2),
week3 = categories.FirstOrDefault(c => c.Record_ID == x.week3)
}));
Try out the following:
var result = (from cd in CustomDatas
join ca1 in Categories on cd.week1 equals ca.Record_ID into ca1r
from ca1 in ca1r.DefaultIfEmpty()
join ca2 in Categories on cd.week2 equals ca.Record_ID into ca2r
from ca2 in ca2r.DefaultIfEmpty()
join ca3 in Categories on cd.week3 equals ca.Record_ID into ca3r
from ca3 in ca3r.DefaultIfEmpty()
select new {
full_name = cd.full_name,
location = cd.location,
week1 = ca1,
week2 = ca2,
week3 = ca3
}
I have a an object Quiz that looks like :
public class Quiz
{
public int Id { get; set; }
public ICollection<MathQuiz> MathQuizzes { get; set; }
}
MathQuizze object looks like :
public class MathQuiz
{
public int Id { get; set; }
public int QuizId{ get; set; }
public Quiz Quiz{ get; set; }
public int AnswerId { get; set; }
public Answer Answer { get; set; }
public int TagId{ get; set; }
public Tag Tag { get; set; }
public bool IsCorrect { get; set; }
}
And have an object(UserQuizzes) that looks like:
public class UserQuizes
{
public int Id { get; set; }
public int UserId { get; set; }
public User User { get; set; }
public int QuizId { get; set; }
public Quiz Quiz { get; set; }
}
UserQuizzes is just class that express many to many relationship between users and quizzes.
This is a sample data :
List<Quiz> quizzes = new List<Quiz>();
quizzes.Add(new Quiz{ Id = 1, MathQuizzes = new List<MathQuiz>{
new MathQuiz { AnswerId = 58, TagId = 1, IsCorrect = false },
new MathQuiz { AnswerId = 26, TagId = 2, IsCorrect = true },
new MathQuiz { AnswerId = 57, TagId = 3, IsCorrect = true },
new Quiz{ Id = 2, MathQuizzes = new List<MathQuiz>{
new MathQuiz { AnswerId = 59, TagId = 1, IsCorrect = false },
new MathQuiz { AnswerId = 87, TagId = 2, IsCorrect = true },
new MathQuiz { AnswerId = 25, TagId = 3, IsCorrect = true }, });
List<UserQuizzes> userQuizzes = new List<UserQuizzes>();
userQuizzes.Add(new Quiz{ QuizId = 1, UserId = 1},
userQuizzes.Add(new Quiz{ QuizId = 2, UserId = 1});
Please don't spend too much time criticizing, I just wanted to use something that everyone is pretty familiar with.
What i want to achieve is that group by userquizzes by MathQuiz TagId and get data something like this:
TagId : 1, IsCorrect: true(0), false(2);
TagId : 2, IsCorrect: true(2), false(0);
TagId : 3, IsCorrect: true(2), false(0);
The code you posted has typos, but here is the basic idea:
var query =
from q in quizzes
from mq in q.MathQuizzes
join uq in userQuizzes on q.Id equals uq.QuizId
group mq by mq.TagId into g
select new
{
TagId = g.Key,
Correct = g.Sum(e => e.IsCorrect ? 1 : 0),
Incorrect = g.Sum(e => e.IsCorrect ? 0 : 1)
};
Basically you need to get the effective source set by joining the data sets, and the do the regular grouping/calculating aggregates.