How to return Generic List with Generic Class Object in c#?

Question

I want to return Table List with there class object and this call also generic, I don't want to use any Non-Strong type List like ArrayList on any other.

        public List<T> GetTables()
        {
            var tbls = new List<T>();
            tbls.Add(new Table<Table1>() { Name = "Table1"});
            tbls.Add(new Table<Table2>() { Name = "Table2"});
            tbls.Add(new Table<Table3>() { Name = "Table3"});
            return tbls;
        }

in above Method, Table1, Table2, and any type table class object... There classes has no any based class, These classes use to Set of table properties with custom format.

I want to return it.

Please help me if anyone have any idea.

thank you.

If they don't all inherit from a common base type and it's not a List<CommonBaseType> then the above is not possible how you want it. Substitute "interface" for "base type" in my prior sentence if we're talking about interfaces. — ProgrammingLlama
– ProgrammingLlama, Commented May 8, 2020 at 6:52

CicheR · Accepted Answer · 2020-05-08 08:12:15Z

2

If the only common thing of the list's components is that they are Table<> generic objects, if there isn't any interface or common base class between Table1/Table2/Table2, you can simply treat them as object:

        public List<Table<IGenerateData>> GetTables()
        {
            var tbls = new List<Table<IGenerateData>>();
            tbls.Add(new Table<Table1>() { Name = "Table1"});
            tbls.Add(new Table<Table2>() { Name = "Table2"});
            tbls.Add(new Table<Table3>() { Name = "Table3"});
            return tbls;
        }

        public interface IGenerateData
        {
            void GenerateData();
        }

        public class Table1 : IGenerateData
        {           
        }

edited May 8, 2020 at 8:12

answered May 8, 2020 at 7:38

CicheR

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3 Comments

Ashish Sojitra Over a year ago

I want to use Strong type, not a Object type.

CicheR Over a year ago

As you suggest on another comment, you need to access the method GenerateData() on Table1 ... Table3... so you can create an Interface IGenerateData with the method, and make Table1 ... Table3 implement that interface. Then your list could be List<Table<IGenerateData>>

Ashish Sojitra Over a year ago

Thanks @CicheR. Based on your idea, Now i can move forward. But still there is an one method i can't access based on above idea. "void GenerateData(T data)" But it not big deal, I can move forward without this method. Thank you again to both of you.

Konstantin Dubrovnyi · Accepted Answer · 2020-05-08 07:03:10Z

1

You can't use generic type with the List without specifying type parameter explicitly. Alternatively, you can create a base class or interface that would be a parameter for the List.

I mean:

        public static List<ITable> GetTables()
        {
            var tbls = new List<ITable>();
            tbls.Add(new Table<Table1> { Name = "Table1"});
            tbls.Add(new Table<Table2> { Name = "Table2"});
            tbls.Add(new Table<Table3> { Name = "Table3"});
            return tbls;
        }

        public class Table<T> : ITable
        {
            public T TableInstance { get; set; }
            public Type TableType => typeof(T);
            public string Name { get; set; }
        }

        public interface ITable
        {
            Type TableType { get; }
            public string Name { get; set; }
        }

answered May 8, 2020 at 7:03

Konstantin Dubrovnyi

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5 Comments

Ashish Sojitra Over a year ago

Thank you @konstanin. but the issue is i still need to pass Table1, table to while accessing "TableInstance". I want this Direct access. I have idea is it possible or not.

Ashish Sojitra Over a year ago

i want like this. public void Run() { var lst = GetTables(); foreach (var item in lst) { item.TableInstance.GenerateData(); } }

Enigmativity Over a year ago

@AshishSojitra - If you want to do that then you must have a common base type or interface.

Ashish Sojitra Over a year ago

Thanks @Konstantin-Dubrovnyi Based on your idea, Now i can move forward. But still there is an one method i can't access based on above idea. "void GenerateData(T data)" But it not big deal, I can move forward without this method. Thank you again to both of you.

Konstantin Dubrovnyi Over a year ago

@AshishSojitra then you may do the following: create base class or interface (ITableInstance) from Table1, Table2, Table3 with method GenerateData(), create List<ITable<ITableIntance>> and use it like you suggested.

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