I have two models Vendors and Users. Each user may or may not have only one Vendor.
Vendors may have several Users.
Models:
public class AppUser
{
public int Id { get; set; }
public string? FullName { get; set; }
public string? Position { get; set; }
public int StatusId { get; set; }
public int VendorId { get; set; }
}
public class Vendor
{
public int VendorId { get; set; }
public string? VendorCode { get; set; }
public string? VendorName { get; set; }
public int StatusId { get; set; }
public List<AppUser> CompanyUsers { get; set; }
}
SQL Tables:
I need to select all Vendors with related Users (if such exists).
My query:
SELECT
v.VendorId
,v.VendorCode
,v.VendorName
,v.Status StatusId
,(CASE
WHEN v.Status = 0 THEN 'Draft'
WHEN v.Status = 1 THEN 'Open'
WHEN v.Status = 2 THEN 'Closed'
WHEN v.Status = 3 THEN 'Blacklisted'
END) StatusName
,au.Id
,au.FullName
,au.Position
,au.StatusId
,(CASE
WHEN au.StatusId = 0 THEN 'Draft'
WHEN au.StatusId = 1 THEN 'Open'
WHEN au.StatusId = 2 THEN 'Closed'
END) StatusName
FROM Procurement.Vendors v
LEFT JOIN Config.AppUser au
ON v.VendorId = au.VendorId
and the result:
Because only Vendor with Id 20 has users, it appears 3 times, which is expected behavior. Now I want to use Dapper's splitOn function to map all users under vendor 20. I split by user's Id column.
public async Task<IEnumerable<Vendor>?> GetAllVendors(int businessUnitId)
{
var currentUser = await _appUserService.GetCurrentUserAsync();
var p = new DynamicParameters();
p.Add("#UserId", currentUser.Id, DbType.Int32, ParameterDirection.Input);
p.Add("#BusinessUnitId", businessUnitId, DbType.Int32, ParameterDirection.Input);
using IDbConnection cn = new SqlConnection(_sqlDataAccess.ConnectionString);
return await cn.QueryAsync<Vendor, AppUser, Vendor>("dbo.SP_ZZZTest",
(vendor, user) =>
{
if (vendor.CompanyUsers == null && user != null) { vendor.CompanyUsers = new(); };
if (user != null) { vendor.CompanyUsers.Add(user); };
return vendor;
},
param: p,
splitOn: "Id",
commandType: CommandType.StoredProcedure);
}
And here is the result I get:
As a result, Dapper did not map Users under a single Vendor. But instead mapped each user as a List of users with a single item duplicating Vendor's data on 3 rows.
What did I wrong?
Yes, this is a common "problem". But it is really simple to solve once you understand the process behind the lambda call.
The lambda expression receives the three records created by the query and before calling the lambda, Dapper splits each record in two at the point of the splitOn configuration. In this process a new Vendor and new AppUser instance will be created for each row processed.
So the Vendor instance received at the second/third call is not the same instance of the first/second call. Dapper doesn't have this kind of processing logic (and I think it is right to avoid it from a performance point of view). So the code above, adds each AppUser to three different instances of Vendor.
It is up to you to 'discover' that the Vendor received contains the same data of a previous call. But it is easy to solve if there is some kind of unique key that identifies a Vendor (the PK of the record)
So this "problem" can be solved using a Dictionary where the key is the PK of the Vendor and you store each unique Vendor data passed by Dapper under that dictionary key. Then you could check if the Vendor data received is already in the Dictionary and use the dictionary instance to add the AppUser.
Dictionary<int, Vendor> result = new Dictionary<int, Vendor>();
.....
using IDbConnection cn = new SqlConnection(_sqlDataAccess.ConnectionString);
_ = await cn.QueryAsync<Vendor, AppUser, Vendor>("dbo.SP_ZZZTest",
(vendor, user) =>
{
if(!result.ContainsKey(vendor.vendorId))
{
vendor.CompanyUsers = new();
result.Add(vendor.vendorId, vendor);
}
Vendor current = result[vendor.vendorId];
if (user != null)
current.CompanyUsers.Add(user);
return vendor;
},
param: p,
splitOn: "Id",
commandType: CommandType.StoredProcedure);
// A VERY IMPORTANT POINT...
// You want to return the Vendors stored in the Values of the
// Dictionary, not the Vendors returned by the QueryAsync call
return result.Values;
Related
I have the following classes:
public class User
{
public int Id { get; set; }
public string Name { get; set; }
public string Department { get; set; }
public List<Event> Events { get; set; }
}
public class Event
{
public int Id { get; set; }
public int UserId { get; set; }
public string EventText { get; set; }
public string StartTime { get; set; }
public string EndTime { get; set; }
public string Day { get; set; }
public string ColorIdentifier { get; set; }
public int Week { get; set; }
}
I'm trying to get all the users and their events with Dapper like this:
var sql = "SELECT u.Id, e.UserId, e.EventText FROM cpc.PLANNING_TOOL_USERS u LEFT JOIN cpc.PLANNING_TOOL_EVENTS e ON u.Id=e.UserId";
var result = SqlMapper.Query<User, Event, User>(connection, sql, (u, e) =>
{
if (u.Events == null)
u.Events = new List<Event>();
u.Events.Add(e);
return u;
}, splitOn: "Id, UserId");
The Id for the user is returned back, but the list of events is not populated. I have looked at many examples here on Stack Overflow regarding this, but I can't see what I'm doing wrong.
To omit the situation that SQL returns no data I have just mocked two user rows with SQL union.
User with Id=1 and one Event, and User with Id=2 and two Events.
SqlMapper.Query returns flat results that are best for 1 to 1 relation. You have one user to many events relation, so some helper storage needed to maintain that relation as a mapping thru the results. I have used .NET dictionary for that.
My code sample below:
// introducing temporary storage
var usersDictionary = new Dictionary<int, User>();
var sql = #"SELECT 1 Id, 1 UserId, 'EventText1' EventText
union SELECT 2 Id, 2 UserId, 'EventText2' EventText
union SELECT 2 Id, 2 UserId, 'Another EventText2' EventText";
var result = SqlMapper.Query<User, Event, User>(connection, sql, (u, e) =>
{
if (!usersDictionary.ContainsKey(u.Id))
usersDictionary.Add(u.Id, u);
var cachedUser = usersDictionary[u.Id];
if (cachedUser.Events == null)
cachedUser.Events = new List<Event>();
cachedUser.Events.Add(e);
return cachedUser;
}, splitOn: "UserId");
// we are not really interested in `result` here
// we are more interested in the `usersDictionary`
var users = usersDictionary.Values.AsList();
Assert.AreEqual(2, users.Count);
Assert.AreEqual(1, users[0].Id);
CollectionAssert.IsNotEmpty(users[0].Events);
Assert.AreEqual(1, users[0].Events.Count);
Assert.AreEqual("EventText1", users[0].Events[0].EventText);
Assert.AreEqual(2, users[1].Events.Count);
I hope that helped you solving your mapping issue and events being null.
I'm attempting to use a CTE with Dapper and multi-mapping to get paged results. I'm hitting an inconvenience with duplicate columns; the CTE is preventing me from having to Name columns for example.
I would like to map the following query onto the following objects, not the mismatch between the column names and properties.
Query:
WITH TempSites AS(
SELECT
[S].[SiteID],
[S].[Name] AS [SiteName],
[S].[Description],
[L].[LocationID],
[L].[Name] AS [LocationName],
[L].[Description] AS [LocationDescription],
[L].[SiteID] AS [LocationSiteID],
[L].[ReportingID]
FROM (
SELECT * FROM [dbo].[Sites] [1_S]
WHERE [1_S].[StatusID] = 0
ORDER BY [1_S].[Name]
OFFSET 10 * (1 - 1) ROWS
FETCH NEXT 10 ROWS ONLY
) S
LEFT JOIN [dbo].[Locations] [L] ON [S].[SiteID] = [L].[SiteID]
),
MaxItems AS (SELECT COUNT(SiteID) AS MaxItems FROM Sites)
SELECT *
FROM TempSites, MaxItems
Objects:
public class Site
{
public int SiteID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public List<Location> Locations { get; internal set; }
}
public class Location
{
public int LocationID { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public Guid ReportingID { get; set; }
public int SiteID { get; set; }
}
For some reason I have it in my head that a naming convention exists which will handle this scenario for me but I can't find mention of it in the docs.
There are more than one issues, let cover them one by one.
CTE duplicate column names:
CTE does not allow duplicate column names, so you have to resolve them using aliases, preferably using some naming convention like in your query attempt.
For some reason I have it in my head that a naming convention exists which will handle this scenario for me but I can't find mention of it in the docs.
You probably had in mind setting the DefaultTypeMap.MatchNamesWithUnderscores property to true, but as code documentation of the property states:
Should column names like User_Id be allowed to match properties/fields like UserId?
apparently this is not the solution. But the issue can easily be solved by introducing a custom naming convention, for instance "{prefix}{propertyName}" (where by default prefix is "{className}_") and implementing it via Dapper's CustomPropertyTypeMap. Here is a helper method which does that:
public static class CustomNameMap
{
public static void SetFor<T>(string prefix = null)
{
if (prefix == null) prefix = typeof(T).Name + "_";
var typeMap = new CustomPropertyTypeMap(typeof(T), (type, name) =>
{
if (name.StartsWith(prefix, StringComparison.OrdinalIgnoreCase))
name = name.Substring(prefix.Length);
return type.GetProperty(name);
});
SqlMapper.SetTypeMap(typeof(T), typeMap);
}
}
Now all you need is to call it (one time):
CustomNameMap.SetFor<Location>();
apply the naming convention to your query:
WITH TempSites AS(
SELECT
[S].[SiteID],
[S].[Name],
[S].[Description],
[L].[LocationID],
[L].[Name] AS [Location_Name],
[L].[Description] AS [Location_Description],
[L].[SiteID] AS [Location_SiteID],
[L].[ReportingID]
FROM (
SELECT * FROM [dbo].[Sites] [1_S]
WHERE [1_S].[StatusID] = 0
ORDER BY [1_S].[Name]
OFFSET 10 * (1 - 1) ROWS
FETCH NEXT 10 ROWS ONLY
) S
LEFT JOIN [dbo].[Locations] [L] ON [S].[SiteID] = [L].[SiteID]
),
MaxItems AS (SELECT COUNT(SiteID) AS MaxItems FROM Sites)
SELECT *
FROM TempSites, MaxItems
and you are done with that part. Of course you can use shorter prefix like "Loc_" if you like.
Mapping the query result to the provided classes:
In this particular case you need to use the Query method overload that allows you to pass Func<TFirst, TSecond, TReturn> map delegate and unitilize the splitOn parameter to specify LocationID as a split column. However that's not enough. Dapper's Multi Mapping feature allows you to split a single row to a several single objects (like LINQ Join) while you need a Site with Location list (like LINQ GroupJoin).
It can be achieved by using the Query method to project into a temporary anonymous type and then use regular LINQ to produce the desired output like this:
var sites = cn.Query(sql, (Site site, Location loc) => new { site, loc }, splitOn: "LocationID")
.GroupBy(e => e.site.SiteID)
.Select(g =>
{
var site = g.First().site;
site.Locations = g.Select(e => e.loc).Where(loc => loc != null).ToList();
return site;
})
.ToList();
where cn is opened SqlConnection and sql is a string holding the above query.
You can map a column name with another attribute using the ColumnAttributeTypeMapper.
See my first comment on the Gist for further details.
You can do the mapping like
public class Site
{
public int SiteID { get; set; }
[Column("SiteName")]
public string Name { get; set; }
public string Description { get; set; }
public List<Location> Locations { get; internal set; }
}
public class Location
{
public int LocationID { get; set; }
[Column("LocationName")]
public string Name { get; set; }
[Column("LocationDescription")]
public string Description { get; set; }
public Guid ReportingID { get; set; }
[Column("LocationSiteID")]
public int SiteID { get; set; }
}
Mapping can be done using either of the following 3 methods
Method 1
Manually set the custom TypeMapper for your Model once as:
Dapper.SqlMapper.SetTypeMap(typeof(Site), new ColumnAttributeTypeMapper<Site>());
Dapper.SqlMapper.SetTypeMap(typeof(Location), new ColumnAttributeTypeMapper<Location>());
Method 2
For class libraries of .NET Framework >= v4.0, you can use PreApplicationStartMethod to register your classes for custom type mapping.
using System.Web;
using Dapper;
[assembly: PreApplicationStartMethod(typeof(YourNamespace.Initiator), "RegisterModels")]
namespace YourNamespace
{
public class Initiator
{
private static void RegisterModels()
{
SqlMapper.SetTypeMap(typeof(Site), new ColumnAttributeTypeMapper<Site>());
SqlMapper.SetTypeMap(typeof(Location), new ColumnAttributeTypeMapper<Location>());
// ...
}
}
}
Method 3
Or you can find the classes to which ColumnAttribute is applied through reflection and set type mappings. This could be a little slower, but it does all the mappings in your assembly automatically for you. Just call RegisterTypeMaps() once your assembly is loaded.
public static void RegisterTypeMaps()
{
var mappedTypes = Assembly.GetAssembly(typeof (Initiator)).GetTypes().Where(
f =>
f.GetProperties().Any(
p =>
p.GetCustomAttributes(false).Any(
a => a.GetType().Name == ColumnAttributeTypeMapper<dynamic>.ColumnAttributeName)));
var mapper = typeof(ColumnAttributeTypeMapper<>);
foreach (var mappedType in mappedTypes)
{
var genericType = mapper.MakeGenericType(new[] { mappedType });
SqlMapper.SetTypeMap(mappedType, Activator.CreateInstance(genericType) as SqlMapper.ITypeMap);
}
}
The below code should work fine for you to load a list of sites with associated locations
var conString="your database connection string here";
using (var conn = new SqlConnection(conString))
{
conn.Open();
string qry = "SELECT S.SiteId, S.Name, S.Description, L.LocationId, L.Name,L.Description,
L.ReportingId
from Site S INNER JOIN
Location L ON S.SiteId=L.SiteId";
var sites = conn.Query<Site, Location, Site>
(qry, (site, loc) => { site.Locations = loc; return site; });
var siteCount = sites.Count();
foreach (Site site in sites)
{
//do something
}
conn.Close();
}
I am implementing an ASP.NET MVC 5 web app using ASP.NET Identity 2 and Troy Goode's PagedList. I need to display UserRole data in the following format in a JqGrid:
User Name | Role Name
This is my UserRole class:
public class UserRole : Microsoft.AspNet.Identity.EntityFramework.IdentityUserRole<int>
{
[ForeignKey("UserId")]
public virtual User User { get; set; }
[ForeignKey("RoleId")]
public virtual Role Role { get; set; }
}
This is my repository method
public virtual IQueryable<UserRole> GetAsQueryable(Expression<Func<UserRole, bool>> where)
{
return _dataContext.UserRoles.Where(where).AsQueryable();
}
This my Controller method (the GetAsPagedList method simply orders the input list, applies PagedList's .ToPagedList method to it and returns a subset of it):
public ActionResult GridData(MvcJqGrid.GridSettings gridSettings)
{
IQueryable<UserRole> items = _repository.GetAsQueryable();
IPagedList<T> pagedOrderedItems = PagingHelper<UserRole>.GetAsPagedList(
items,
gridSettings.SortOrder, gridSettings.SortColumn,
gridSettings.PageIndex, gridSettings.PageSize);
var jsonData = new
{
total = pagedOrderedItems.TotalItemCount / gridSettings.PageSize + 1,
page = gridSettings.PageIndex,
records = pagedOrderedItems.TotalItemCount,
rows = (
from c in pagedOrderedItems
select new
{
id = c.UserId + '-' + c.RoleId,
cell = new[]
{
"Edit",
"Details",
// TODO: something like this:
// [UserName] = c.User.UserName
// [RoleName] = c.Role.Name
c.Role.Name
}
}).ToArray()
};
return Json(jsonData, JsonRequestBehavior.AllowGet);
}
I can'.t figure out where and how I should deep load data from the tables linked through foreign keys to my table (I.E. Users.UserName and Roles.Name) - could you please help?
_dataContext.UserRoles.Include("Role").Include("User").Where(where).AsQueryable();
I have a Product table that has no relation defined to the translation table. I added a Translation property to the Product POCO as [NotMapped].
**My Product POCO: **
public partial class Product
{
public int ProductID { get; set; }
public double Price { get; set; }
[NotMapped]
public virtual Translation Translation{ get; set; }
/** Other properties **/
}
I also have a Translation table, and like the name says, it contains all the translations.
Now, the right translation can be retrieved from the database by providing three parameters: LanguageID, TranslationOriginID and ValueID.
LanguageID: ID from the language that the user has defined.
TranslationOriginID: Simply said, 'What table contains the entity that I want the translation for?' In other words, this ID points to another table that contains all possible origins. An origin is a table/entity that can have a translation. E.g: The origin in this example is Product.
ValueID: This is the ID of the entity that I want a translation for.
My Translation POCO:
public partial class Translation
{
public int TranslationID { get; set; }
public byte LanguageID { get; set; }
public short TranslationOriginID { get; set; }
public int ValueID { get; set; }
public string TranslationValue { get; set; }
/** Other properties **/
public virtual TranslationOrigin TranslationOrigin { get; set; }
public virtual Language Language { get; set; }
}
When I want to retrieve all products with their Translation, I execute this code:
List<Product> products = context.Products.ToList();
foreach (Product product in products)
{
product.Translation = context.Translations.FirstOrDefault(y => y.LanguageID == 1 && y.TranslationOriginID == 2 && y.ValueID == product.ProductID);
}
Like you can see, I execute for every product in the list another query to get the translation.
My question:
Is it possible to get all the products and their translation in one query? Or even that I automatically retrieve the right translation when I select a product?
I already tried an .Include() and a .Select(). It didn't work, maybe I did something wrong?
I also tried this method, didn't work either.
Btw, I use Entity framework 5 with .NET 4 (so, Entity Framework 4.4).
Thanks in advance.
Greetings
Loetn
Answer
With the example given by Ed Chapel, I came up with a solution.
return (from p in context.Products
join t in context.Translations
on new
{
Id = p.ProductID,
langId = languageID,
tOriginId = translationOriginID
}
equals new
{
Id = d.ValueID,
langId = d.LanguageID,
tOriginId = d.TranslationOriginID
}
into other
from x in other.DefaultIfEmpty()
select new
{
Product = p,
Translation = x
})
.ToList().ConvertAll(x => new Product()
{
Code = x.Product.Code,
Translation = x.Translation,
/** Other properties **/
});
I don't like proper LINQ in most cases. However, join is one scenario where the LINQ is easy than the extensions methods:
from p in context.Products
join t in context.Translations
on t.ValueID equals p.ValueID
&& t.LanguageID == 1
&& t.TranslationOriginID == 2
into joinT
from x in joinT
select new {
Product = p,
Translation = t,
};
You then loop over the result setting x.Product.Translation = x.Translation.
First of all you should realize that your translations table is not structured like a dba would like it You have a non enforced relationship because depending on the OriginId your valueId references a different table.
Because of this you cannot use lazy loading or includes from EF.
My best idea at this point would to manually join the table on an anonymous type(to include your originId). Afterwards you can iterate over the results to set the translation property
The result would look like this :
var data = from p in context.Products
join pt in context.Translations on new{p.Id,2} equals new {pt.ValueId, pt.OriginId} into trans
select new {p, trans};
var result = data.ToList().Select( a =>
{
a.p.Translations = a.trans;
return a.p;
}).ToList();
With the example that Ed Chapel proposed as a solution, I came up with this.
return (from p in context.Products
join t in context.Translations
on new
{
Id = p.ProductID,
langId = languageID,
tOriginId = translationOriginID
}
equals new
{
Id = d.ValueID,
langId = d.LanguageID,
tOriginId = d.TranslationOriginID
}
into other
from x in other.DefaultIfEmpty()
select new
{
Product = p,
Translation = x
})
.ToList().ConvertAll(x => new Product()
{
Code = x.Product.Code,
Translation = x.Translation,
/** Other properties **/
});
I'm creating a product listing for an online store. It's pretty standard stuff, a page of product thumbnails with brief details, price and a link through to full details.
I'm using a repository pattern, so I have a central data repository which gives me back tables from a SQL server. I've cut a lot of the code out for the sake of brevity, but just so you get the idea:
public class SqlProductsRepository : IProductsRepository
{
private Table<Product> productsTable;
public SqlProductsRepository(string connectionString)
{
var context = new DataContext(connectionString);
productsTable = context.GetTable<Product>();
// More tables set up here
}
public IQueryable<Product> Products
{
get { return productsTable; }
}
// More properties here
}
I have the following objects mapped to tables:
[Table(Name = "Products")]
public class Product
{
[Column(IsPrimaryKey = true)]
public string ProductCode { get; set; }
[Column]
public string Name { get; set; }
[Column]
public decimal Price { get; set; }
public List<ShopImage> Images = new List<ShopImage>();
}
[Table(Name = "Images_Products")]
public class Image_Product
{
[Column]
public int ImageID { get; set; }
[Column]
public string ProductCode { get; set; }
[Column]
public int DisplayOrder { get; set; }
}
[Table(Name = "Images")]
public class Image
{
[Column(Name = "ImageID")]
public int ImageID { get; set; }
[Column]
public bool Caption { get; set; }
}
If I perform the following query:
// 'db' is the repository (member variable of the controller class)
IQueryable<Product> products = from p in db.Products
join ip in db.Image_Product on p.ProductCode equals ip.ProductCode
where ip.DisplayOrder == 0
select p;
I get a nice IQueryable full of Product objects. However, what I want to do is populate each object's Images list property with a single Image object, with its ID set from the joined Image_Product table.
So I end up with a list of Products, each with one Image in its Images property, which has the ID of the image for that product in the database where DisplayOrder is 0.
I tried this projection, which I thought made sense:
IQueryable<Product> products = from p in db.Products
join ip in db.Image_Product on p.ProductCode equals ip.ProductCode
where ip.DisplayOrder == 0
select new Product {
ProductCode = p.ProductCode,
Price = p.Price,
Images = new List<Image> {
new Image { ImageID = ip.ImageID }
}
};
Which compiles, but throws a runtime error: Explicit construction of entity type 'xxx.Product' in query is not allowed.
Yet elsewhere in the project I do this:
var pages = from i in db.TemplatePageNavigationItems
orderby i.DisplayOrder
select new NavigationItem {
ID = i.PageID,
ParentID = i.ParentID,
Text = i.Name,
Title = i.Name,
Url = (i.Folder == null) ? "" : i.Folder
};
And get no complaints! I assume it's something to do with the first query returning an IQueryable<Product> but I'm not sure why.
Two questions really: why is this not allowed in the first situation, and what should I be doing in order to get my desired result?
As the error says, you can't construct explicit entity types (Product is just that) in your query which should return IQueryable<Product>. Your pages query will return IEnumerable<NavigationItem> and NavigationItem does not seem to be an entity type defined in the database.
You could try returning IEnumerable<Product> in your first query or define a separate type and return IEnumerable of that instead, if you need to project explicit, custom tailored instances of an object.