Anyone know how to pass the IEnumerable<xxxxx> into method. XXXXX is refer to any class.
I want to make it dynamic to accept any class. Example, <student>, <course>, <semester>, etc.
Currently it is fixed as Employee class.
public IEnumerable<Employee> GetJsonFile(string strFolder, string strFileName)
{
string strFile = Path.Combine(WebHostEnvironment.WebRootPath, strFolder, strFileName);
using (var jsonFileReader = File.OpenText(strFile))
{
return JsonSerializer.Deserialize<Employee[]>(jsonFileReader.ReadToEnd(), new JsonSerializerOptions { PropertyNameCaseInsensitive = true});
}
}
Use Generics. IEnumerable<T> Where T is a class.
Generics Guide
Instead of using <Employee> use <T>
public IEnumerable<T> GetJsonFile<T>(string strFolder, string strFileName)
{
...return JsonSerializer.Deserialize<T[]>...
}
Then when you call the method you supply it with the type.
var x = GetJsonFile<student>(folder,file);
For more information lookup information on C# Generics.
Related
I have a stored procedure that returns me a list of IDs. (I then use this list of IDs as keys for objects.)
I am migrating this from .NET to .NET Core. In normal .NET I could use an extension library to get the numbers out like this:
var getOrderDetailIdsStoredProc = new GetOrderDetailIdsStoredProc()
{
NumberOfOrderDetailIdsNeeded = numberOfOrderDetailIdsNeeded
};
var orderDetailIds = contextProvider.Context.Database
.ExecuteStoredProcedure<long>(getOrderDetailIdsStoredProc);
But that library (EntityFrameworkExtras) is not working with EF Core (I found a version for EF Core, but it doesn't work.)
So I have been looking for other solutions:
DbContext.Database.ExecuteSqlCommand: Cannot return records, only output variables
DbSet.FromSQL: Can only be run on a DbSet<T> (basically it needs an entity type)
Right now, all I can think of is to make an entity called Number:
public class Number
{
public long Value;
}
public DbSet<Number> Numbers;
And then do something like this:
Numbers.FromSql("exec GenerateOrderDetailSequencedIds #numberNeeded", numberNeeded)
Aside from the fact that this is very ugly (making an entity out of a native type), I have no table to hook it up to, so I worry it will not work.
Is there any way in EF Core to run a stored procedure and get back a list of numbers?
NOTE: This worked, but was not compatable with BreezeJs (it could not deal with a DbQuery). See my other answer for what I ended up doing.
OrderDetailIdHolder.cs
public class OrderDetailIdHolder
{
public long NewId { get; set; }
}
MyEntitiesContext
public DbQuery<OrderDetailIdHolder> OrderDetailIdHolders { get; set; }
internal List<long> GetOrderDetailIds(int numberOfIdsNeeded)
{
var result = OrderDetailIdHolders.FromSql($"exec Sales.GenerateOrderDetailIds {numberOfIdsNeeded}").ToList();
return result.Select(x=>x.NewId).ToList();
}
This a bit extra complexity for just a list of longs. But it works.
It is important to note that the property (NewId in this case) must match what is returned from the sproc. Also, the type is not a DbSet. It is a DbQuery.
It is also important to note that this is only for EF Core 2.2. EF Core 3 has a different way to do this (Keyless Entity Types)
This is what I ended up using:
public static List<T> SqlQueryList<T>(this DatabaseFacade database, string query, params SqlParameter[] sqlParameters)
{
// TODO: Add a using statement here so we don't leak the connection's resources.
var conn = database.GetDbConnection();
conn.Open();
var command = conn.CreateCommand();
command.CommandText = query;
command.Parameters.AddRange(sqlParameters);
var reader = command.ExecuteReader();
List<T> result = new List<T>();
while (reader.Read())
{
T typedRow;
var row = reader.GetValue(0);
if (typeof(T).IsValueType)
{
typedRow = (T) row;
}
else
{
typedRow = (T)Convert.ChangeType(result, typeof(T));
}
result.Add(typedRow);
}
return result;
}
Called like this:
var numberOfOrderDetailIdsNeededParam = new SqlParameter
{
ParameterName = "#numberOfOrderDetailIdsNeeded",
SqlDbType = SqlDbType.Int,
Direction = ParameterDirection.Input
};
numberOfOrderDetailIdsNeededParam.Value = numberOfOrderDetailIdsNeeded;
var result = contextProvider.Context.Database.SqlQueryList<long>($"exec Sales.GenerateOrderDetailIds #numberOfOrderDetailIdsNeeded", numberOfOrderDetailIdsNeededParam);
I did it this way because it was compatible with BreezeJs for .NET Core. Note that I only really tested this with Value types.
I'm using Specification pattern in EF Code First. When I do order by operation, VS throw a new exception
The specification pattern is copy from eShopOnWeb
I just change a little bit, here is my change code:
public class Specification<T> : ISpecification<T>
{
public Expression<Func<T, object>> OrderBy { get; private set; }
public Specification(Expression<Func<T, bool>> criteria)
{
Criteria = criteria;
}
public Specification<T> OrderByFunc(Expression<Func<T, object>> orderByExpression)
{
OrderBy = orderByExpression;
return this;
}
}
Here is my invoke code, it's very pretty simple:
static void TestSpec()
{
var spec = new Specification<ExcelData>(x => x.RowIndex == 5)
.OrderByFunc(x => x.ColumnIndex);
using (var dbContext = new TechDbContext())
{
var top10Data = dbContext.ExcelData.Take(10).ToList();
var listExcel = dbContext.ApplySpecification(spec).ToList();
Console.WriteLine();
}
}
If I comment OrderByFunc, then everything is fine to me. no error throw from vs.
I had try many times search the error message in google, but none of answer is my case.
So I have to ask a question in here.
When I debug OrderBy property in SpecificationEvaluator.cs, I found there is a Convert method.
So I know the error is about cast error, but how do I fix this cast type error?
Please help me!
The solution is to create new lambda expression with cast (Convert) removed, and then use it to call the Queryable class OrderBy / OrderByDescending method either dynamically (using DLR dispatch or reflection) or by emitting Expression.Call to it.
For the first part, add the following helper method to the SpecificationEvaluator class:
static LambdaExpression RemoveConvert(LambdaExpression source)
{
var body = source.Body;
while (body.NodeType == ExpressionType.Convert)
body = ((UnaryExpression)body).Operand;
return Expression.Lambda(body, source.Parameters);
}
Then replace the code
query = query.OrderBy(specification.OrderBy);
with either
query = Queryable.OrderBy((dynamic)query, (dynamic)RemoveConvert(specification.OrderBy));
or
var keySelector = RemoveConvert(specification.OrderBy);
query = query.Provider.CreateQuery<T>(Expression.Call(
typeof(Queryable), nameof(Queryable.OrderBy),
new[] { typeof(T), keySelector.ReturnType },
query.Expression, keySelector));
Do similar for the specification.OrderByDescending.
I have a pojo that contains a property name, logic operator as String and the value of property. What I want to accomplish is create a Predicate or Expression etc dynamically from the pojo data. Below are my code:
public class QueryParam {
private String property = "acctType"; //can be any property of classname
private String operator = "eqic" //can be any logic operator !=, >, <, >=, <= etc
private Object value; //will store the value of
// getters/setters here
}
public interface CustomerRepository extends JpaRepository<Customer, Long>, QueryDslPredicateExecutor<Customer>{
}
#Service("CustomerService")
class MyCustomerServiceImpl {
#Resource
private CustomerRepository custRpstry;
//if classname is Customer, property is "acctType", operator is "eqic", and value is "Corporate"
//I want my findAll below to retrieve all Customers having acctType = "Corporate"
List<Customer> findAll(List<QueryParam> qryParam) {
QCustomer qcust = QCustomer.customer;
BooleanBuilder where = new BooleanBuilder();
for(QueryParam param : qryParam) {
//within this block, i want a BooleanBuilder to resolve to:
where.and(qcust.acctType.equalsIgnoreCase("Corporate"));
something like:
where.and(param.getClassname().param.getProperty().param.getOperator().param.getValue())
}
return custRpstry.findAll(where.getValue()).getContent();
}
}
I can't figure out to formulate my BooleanBuilder especially the portion that will convert
getOperator() into .equalIgnoreCase().
Any help would be greatly appreciated.
Thanks in advance,
Mario
After combining several answers to some related questions here in so, I was able to formulate a solution that works for me.
BooleanBuilder where = new BooleanBuilder();
for(QueryParam param: qryParam) {
//create: Expressions.predicate(Operator<Boolean> opr, StringPath sp, filter value)
//create an Operator<Boolean>
Operator<Boolean> opr = OperationUtils.getOperator(param.getOperator().getValue());
//create a StringPath to a class' property
Path<User> entityPath = Expressions.path(Customer.class, "customer");
Path<String> propPath = Expressions.path(String.class, entityPath, param.getProperty());
//create Predicate expression
Predicate predicate = Expressions.predicate(opr, propPath, Expressions.constant(param.getValue()));
where.and(predicate);
}
list = repository.findAll(where.getValue(), pageReq).getContent();
My OperationUtils.java
public class OperationUtils {
public static com.mysema.query.types.Operator<Boolean> getOperator(String key) {
Map<String, com.mysema.query.types.Operator<Boolean>> operators = ImmutableMap.<String, com.mysema.query.types.Operator<Boolean>>builder()
.put(Operator.EQ.getValue() ,Ops.EQ)
.put(Operator.NE.getValue() ,Ops.NE)
.put(Operator.GT.getValue() ,Ops.GT)
.put(Operator.GTE.getValue() ,Ops.GOE)
.put(Operator.LT.getValue() ,Ops.LT)
.put(Operator.LTE.getValue() ,Ops.LOE)
.build();
return operators.get(key);
}
}
I am using aspectj to add some field to a existing class and annotate it also.
I am using load time weaving .
Example :- I have a Class customer in which i am adding 3 string attributes. But my issues is that I have to set some values and get it also before my business call.
I am trying the below approach.
In my aj file i have added the below, my problem is in the Around pointcut , how do i get the attribute and set the attribute.
public String net.customers.PersonCustomer.getOfflineRiskCategory() {
return OfflineRiskCategory;
}
public void net.customers.PersonCustomer.setOfflineRiskCategory(String offlineRiskCategory) {
OfflineRiskCategory = offlineRiskCategory;
}
public String net.customers.PersonCustomer.getOnlineRiskCategory() {
return OnlineRiskCategory;
}
public void net.customers.PersonCustomer.setOnlineRiskCategory(String onlineRiskCategory) {
OnlineRiskCategory = onlineRiskCategory;
}
public String net.customers.PersonCustomer.getPersonCommercialStatus() {
return PersonCommercialStatus;
}
public void net.customers.PersonCustomer.setPersonCommercialStatus(String personCommercialStatus) {
PersonCommercialStatus = personCommercialStatus;
}
#Around("execution(* net.xxx.xxx.xxx.DataMigration.populateMap(..))")
public Object invoke(ProceedingJoinPoint joinPoint) throws Throwable {
Object arguments[] = joinPoint.getArgs();
if (arguments != null) {
HashMap<String, String> hMap = (HashMap) arguments[0];
PersonCustomer cus = (PersonCustomer) arguments[1];
return joinPoint.proceed();
}
If anyone has ideas please let me know.
regards,
FT
First suggestion, I would avoid mixing code-style aspectj with annotation-style. Ie- instead of #Around, use around.
Second, instead of getting the arguments from the joinPoint, you should bind them in the pointcut:
Object around(Map map, PersonCustomer cust) :
execution(* net.xxx.xxx.xxx.DataMigration.populateMap(Map, PersonCustomer) && args(map, cust) {
...
return proceed(map, cust);
}
Now, to answer your question: you also need to use intertype declarations to add new fields to your class, so do something like this:
private String net.customers.PersonCustomer.OfflineRiskCategory;
private String net.customers.PersonCustomer.OnlineRiskCategory;
private String net.customers.PersonCustomer.PersonCommercialStatus;
Note that the private keyword here means private to the aspect, not to the class that you declare it on.
Recently i was asked to prove the power of C# 3.0 in a single line( might be tricky)
i wrote
new int[] { 1, 2, 3 }.Union(new int[]{10,23,45}).
ToList().ForEach(x => Console.WriteLine(x));
and explained you can have (i) anonymous array (ii) extension method (iii)lambda and closure all in a single line.I got spot offer.
But.....
The interviewer asked me how will you convert an anonymous type into known type :(
I explained
public class Product
{
public double ItemPrice { private set; get; }
public string ItemName { private set; get; }
}
var anony=new {ItemName="xxxx",ItemPrice=123.56};
you can't assign product a=anony;
The interviewer replied there is 200% chance to do that
if you have a small work around.I was clueless.
As usual,I am waiting for your valuable reply(Is it possible?).
You're right, you can't make this assignment:
product a=anony;
MSDN: Anonymous Types (C# Programming Guide)
An anonymous type cannot be cast to
any interface or type except for
object.
Maybe something like this:
class Program
{
static T Cast<T>(object target, T example)
{
return (T)target;
}
static object GetAnon()
{
return new { Id = 5 };
}
static void Main()
{
object anon = GetAnon();
var p = Cast(anon, new { Id = 0 });
Console.WriteLine(p.Id);
}
}
Remark: never write or rely on such a code.
May be try the examples shown here..they try to do something similar..
http://www.codeproject.com/KB/linq/AnonymousTypeTransform.aspx
http://www.inflecto.co.uk/Inflecto-Blog/post/2009/11/12/IQueryable-Sorting-Paging-Searching-and-Counting.aspx
var list = anony.Select(x=> new Product {
ItemPrice = x.ItemPrice, ItemName = x.ItemName }).ToList();