In this case, you don't need it. We will learn the following things in this article: Creating Excel file using C# Writing data to cells Formatting data to cells During deserialization, you have to find clues that identify the required type in the JSON. Developers use AI tools, they just dont trust them (Ep. Do large language models know what they are talking about? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. first of all thanks a lot for your cooperation. You would also get to see Unchecked Cast warning which informs you about the presence of cast from a generic type to a non-qualified type or the vice versa. Find centralized, trusted content and collaborate around the technologies you use most. Program where I earned my Master's is changing its name in 2023-2024. The following code shows an example for this scenario: Here are the Employee and Company classes: A class that derives from ReferenceResolver stores the references in a dictionary: A class that derives from ReferenceHandler holds an instance of MyReferenceResolver and creates a new instance only when needed (in a method named Reset in this example): When the sample code calls the serializer, it uses a JsonSerializerOptions instance in which the ReferenceHandler property is set to an instance of MyReferenceHandler. To create an instance of a generic type, you need the new()-constraint on it. Even if all the contents of the list are of String, the List is still a List
, so you cannot do a direct cast like that. How do I convert from List<?> to List<T> in Java using generics? Does the DM need to declare a Natural 20? Step 1: Create the generic list classThis class will hold our generic list items. Convert a raw List to a generic List Overview Overview Example Overview While refactoring old code, you might have already encountered that the classes are inundated with lots of non-generic List. 6 Answers Sorted by: 59 groupMembers.Cast<object> ().ToList (); But that doesn't look a good thing to do. Find centralized, trusted content and collaborate around the technologies you use most. What are the advantages and disadvantages of making types as a first class value? ).In the following code, I'd like to use List<T>-specific functionality, such as Linq functions.. With the following check, I make sure, it's a list: However, the main problem is my project already developed based on SQL server, and factory pattern is being used in my project. But I took the hint from your answer and instead of sending List as T I used List and let the conversion handled in the caller Main() as follows. The following sections provide converter samples that address some common scenarios that built-in functionality doesn't handle. Any help or suggestion is appreciated. There is no way to directly convert from one type to the other without making an entirely new set of objects. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, It's theoretically possible, but needs a lot of awkward reflection. I've got a data structure in which a variable is of type object.However, I know during runtime this object will be definitely a List<T>, where T should cover multiple cases (e.g., int, string, . How to Convert a generic type list of data to another generic type list For a sample DataTable converter, see Supported collection types. Convert a Sequence to a Generic List - ADO.NET | Microsoft Learn The following sample uses ToList to immediately evaluate a query into a generic List<T>.. var empQuery = from emp in db.Employees where emp.HireDate >= new DateTime(1994, 1, 1) select emp; List<Employee> qList = empQuery.ToList(); Does the DM need to declare a Natural 20? Is it okay to have misleading struct and function names for the sake of encapsulation? The following code shows a base class, two derived classes, and a custom converter for them. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. select new MyClass() { X = p.x, Y = P.y }).ToList(); The former create a list of an anonymous class, the second creates a list of MyClass objects. Views: 14464. Connect and share knowledge within a single location that is structured and easy to search. By requiring someone to bind to a specific type, you take some of the guesswork out and things tend to go smoother. I used to spend way too much time messing with generics over the years. Asking for help, clarification, or responding to other answers. Should I sell stocks that are performing well or poorly first? As an alternative, you might try the "out-param" approach: This one can't incur the run-time exception if destType isn't compatible with List> and saves you a bit of casting. The following example shows a Read method that uses this alternative: If you deserialize a JSON string into a Stack object and then serialize that object, the contents of the stack are in reverse order. Sample Code: Download. Now let us start with a step by step approach from the creation of a simple MVC application as in the following: "Start", then "All Programs" and select "Microsoft Visual Studio 2015". Convert A Generic List To CSV File In C# Clint McMahon Feb 7, 2020 1 min read This is an example of how to convert a generic list to a dynamic downloadable .csv file using C#, the CsvHelper library and the FileStreamResult. You should not repeat any lines in code, this means defeat the purpose of programming. 1 is very useful and working fine. The unit test below shows the code inside a unit test. To learn more, see our tips on writing great answers. Draw the initial positions of Mlkky pins in ASCII art, JVM bytecode instruction struct with serializer & parser, Lifetime components in phosphorescence decay. How Did Old Testament Prophets "Earn Their Bread"? 586), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Temporary policy: Generative AI (e.g., ChatGPT) is banned, Transforming a generic list of one type to another type, where the types are only known at runtime, C# Generics typecast List to List< BaseType>, How To Cast Generic List of One Type To Generic List of an Unknown Type, Convert List to List, Type is known at runtime, How to use reflection to get generic lists of a particular type, Convert from generic list to specific list using reflection, Convert Type object to Type of List. Example For example, a discriminator property might be available or you might have to rely on the presence or absence of a particular property. @Md.SabbirAhamed, as I am not familiar with whole picture, it is possible that adding, Yes, I am happy that problem is solved :). Does "discord" mean disagreement as the name of an application for online conversation? For example, System.Type is not supported for security reasons, so an attempt to deserialize it results in a NotSupportedException. Making statements based on opinion; back them up with references or personal experience. A converter for an open generic type (List, for example) has to create a converter for a closed generic type (List, for example) behind the scenes. Unfortunately, I've found nothing helpful on the Web. If you throw a NotSupportedException, you always get the path information in the message. However, should i use reflection to solve the problem or there is a better way to introduce EF in my project? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. For example, you might want, To support a custom value type. The thing is, the object is the known type but I pass it as an object.How do I convert it to the known type without knowing what it is? what happens when someone decides to name their class String?). convert list of objects to list of strings and generics. For instance, why does Croatia feel so safe? More info about Internet Explorer and Microsoft Edge, How to serialize and deserialize JSON in .NET, DateTime and DateTimeOffset support in System.Text.Json, Deserialize inferred types to object properties, Support enum string value deserialization, polymorphic serialization and deserialization, Migrate from Newtonsoft.Json to System.Text.Json, Int32 converter that converts null to 0 on deserialize, Int32 converter that allows both string and number values on deserialize, List converter that accepts external data, Long[] converter that works with a comma-delimited list of numbers, the source code of the existing converter, To override the default behavior of a built-in converter. I haven't done DB First with EF so I can't comment on it. How to cast a list of specific type to a list of generic type in c#, How to convert one generic list to another, Conversion of object List to Generic List. The following example demonstrates the ToArray method and other methods of the List<T> class that act on ranges. I think the best option you tried is entities = list.ConvertAll(x => new TVm(x));.The reason it fails compilation is that, in C# inherited classes doesn't necessarily need to have same constructor as base class.Instead you should initialize TVm inside BaseService.Additionally, your try catch block does nothing more than losing some data and affecting StackTrace, so you better remove it. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. As a result, i have followed DB first approach as i already have data tables. Chances are that any one-line solution is just executing a loop internally anyway. How do they capture these images where the ground and background blend together seamlessly? Very good. If the deserializer parses a JSON number that has no decimal point as a long, that might result in out-of-range issues if the value was originally serialized as a ulong or BigInteger. C# insert List<List<object>> in datatable and then to sql Best way to insert a list of objects into a sql #temp table and then do Parsing a number that has a decimal point as a double might lose precision if the number was originally serialized as a decimal. One common use case is to serialize and deserialize a list of POJOs. In the ExportToCSV action method, we get a list of students from the database using the entity framework and convert it into a list of objects. Would the Earth and Moon still have tides after the Earth tidally locks to the Moon? This is an example of how to convert a generic list to a dynamic downloadable .csv file using C#, the CsvHelper library and the FileStreamResult. Did COVID-19 come to Italy months before the pandemic was declared? Reflection is slow, first of all. How can we compare expressive power between two Turing-complete languages? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. It is important for a codebase to evolve and thats why I would like to discuss about how to refactor your old non-generic List to generic List. How can I convert a generic List to a List? Can an open and closed function be neither injective or surjective. Should X, if theres no evidence for X, be given a non zero probability? Provide an answer or move on to the next question. Instead you should initialize TVm inside BaseService. Suppose, for example, you have a Person abstract base class, with Employee and Customer derived classes. Understand that English isn't everyone's first language so be lenient of bad
Use the clone to read through the discriminator tokens. In some scenarios, you might want to use the default system converter in a custom converter. For instance, I want to convert also Agent to agent2. How to convert IEnumerable to List and List back to IEnumerable in C#? Currently, user properties need to be managed through the Azure Portal. Background story: I want to get data from influxdb and copy this data to SQL table and I want to do this with a datatable. But, with Code First, yes, you can call your classes whatever you want. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, The future of collective knowledge sharing, could you add the code that you use (or at least the snippets that allude to the strongly typed list, But all I know is the Type, not the class name :(, @deccks but the type IS the class name. Is it okay to have misleading struct and function names for the sake of encapsulation? In fact, if the extension methods didn't exist, you could write your own. Csharp Server Side Programming Programming IEnumerable is an interface defining a single method GetEnumerator () that returns an IEnumerator interface. Why are the perceived safety of some country and the actual safety not strongly correlated? The following code shows a custom converter that works with Dictionary. List of Objects. Anyway, I answered your question, haven't I? Are throat strikes much more dangerous than other acts of violence (that are legal in say MMA/UFC)? To learn more, see our tips on writing great answers. Upon execution (button click), the data in the list of objects should be stored into a temporary table and the values cross checked and subsequently if data does not exist, these data from the temp table should be inserted, otherwise, updated and if the data in the existing table does not exist in the temp table, then the data should be deleted . How do I distinguish between chords going 'up' and chords going 'down' when writing a harmony? The converter is automatically used on the TemperatureCelsius property of the following type when you serialize or deserialize it: During serialization or deserialization, a converter is chosen for each JSON element in the following order, listed from highest priority to lowest: If multiple custom converters for a type are registered in the Converters collection, the first converter that returns true for CanConvert is used. There's several ways you can do that, but here's one way: It's a little messy, as you have to give it a primitive data type and then cast it back, but it works. An alternative is to call Deserialize or Serialize to do some of the work. Please see my comment to the question and Solution 2. The reason it fails compilation is that, in C# inherited classes doesn't necessarily need to have same constructor as base class. The following code shows a custom converter that enables round-tripping to and from Stack objects: By default, the built-in JsonStringEnumConverter can serialize and deserialize string values for enums. Chances are they have and don't get it. Set permission set assignment expiration by a code or a script? Now my problem is this: To learn more, see our tips on writing great answers. The example then creates a List<T> of PointF structures, creates a Converter\<PointF, Point> delegate (Converter(Of PointF, Point) in Visual Basic) to represent the PointFToPoint method, and passes the delegate to the ConvertAll method. Apex just doesn't have very robust support for generics. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Here, you can clearly see to cast a generic, , we have to take 2 steps. Would the Earth and Moon still have tides after the Earth tidally locks to the Moon? Step 1: Create a console application and add the Student class with the properties as below. 586), Starting the Prompt Design Site: A New Home in our Stack Exchange Neighborhood, Testing native, sponsored banner ads on Stack Overflow (starting July 6), Temporary policy: Generative AI (e.g., ChatGPT) is banned. Connect and share knowledge within a single location that is structured and easy to search. Use ToList to create a generic List from a sequence.. Then we created a Name of Columns from the model property and inserted it into the first index of the students' list. A tag already exists with the provided branch name. C# MVC List To CSV File - GitHub Thank you! var y = (from p in. For instance, why does Croatia feel so safe? The purpose is because I am writing a business data layer for my project that all you have to do is name your class and properties the same name as entities in your database and the data layer will automatically populate referenced tables as types that are declared in the class. Find centralized, trusted content and collaborate around the technologies you use most. Set permission set assignment expiration by a code or a script? The following sample is a converter that overrides default serialization for an existing data type. Yes, you are right. The unit tests folder in the System.Text.Json.Serialization source code includes other custom converter samples, such as: If you need to make a converter that modifies the behavior of an existing built-in converter, you can get the source code of the existing converter to serve as a starting point for customization.
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