class Test
{
   string mFileName;
   File mFile;

   Test Set_FileName(pFileName)
   {
      Test res = *this;
      res.mFileName = pFileName;
      return res;
   }

   void Init ()
   {
      mFile = FileOpen(mFileName);
   }
};

int main() {
    Test t = Test().Set_FileName("foo.txt").Init();
}

The new constraint specifies that a type argument in a generic class or method declaration must have a public parameterless constructor.
— https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/keywords/new-constraint

CWnd w;
w.Create(NULL, "Hello");

class FooBuilder
{
public:

Foo Build()
  {
     Foo f; // конструктор без параметров по условию
     // тут что?    
     return f;
  }
};

  something=di.GetSomething()

Есть известный шаблон IDisposable, который предназначен для освобождения ресурсов.
Он нужен по той причине, что деструктор (финализатор) не всегда корректно справляется со своей "работой".
...аналогичный по схеме IDisposable, но противоположный по значению.

using (new AResource(resourceConfig)) 
{
  // ...
}

using (resourceConfig.CreateAResource()) 
{
  // ...
}

тут думаю лучше обойтись без наследования, даже если разные params_ имеют одинаковые поля
чтобы было легче дорабатывать. Плюс за наглядность, чтобы не искать в исходниках базу

struct params_car_holder (text name, float size, agent orange)

// метод-аксесор
params_car_holder::get_age() { return this.orange.calc(this.size) }

Система
  Ресурсы
  Обработчики

class Test
{
   string mFileName;
   File mFile;

   void Set_FileName (pFileName)
   {
      mFileName = pFileName;
   }

   void Init ()
   {
      mFile = FileOpen(mFileName);
   }
};

lTest = new Test;
lTest.Set_FileName("c:\test_file.txt")
lTest.Init();

class Test
{
   string mFileName;
   File mFile;

   void Set_FileName (pFileName)
   {
      mFileName = pFileName;
   }

   void Init ()
   {
      mFile = FileOpen(mFileName);
   }
};

lTest = new Test;
lTest.Set_FileName("c:\test_file.txt")
lTest.Init();

class Car ( int wheels, float max_speed )

class Test ( string path, file handle )

// фабрика
class maker ()

maker::new_car(int wheels, float max_speed)
{
  ret = new Car;
  ret.wheels = wheels;
  ret.max_speed = max_speed;
  return ret;
}

maker::new_test(string path)
{
  ret = new Test;
  ret.path = path;
  ret.handle = CreateFile(path);
  return ret;
}

// фабрика
class maker (

  Car new_car(int wheels, float max_speed)
  {
    ret = new Car;
    ret.wheels = wheels;
    ret.max_speed = max_speed;
    return ret;
  }

  Test new_test(string path)
  {
    ret = new Test;
    ret.path = path;
    ret.handle = CreateFile(path);
    return ret;
  }
)

lStr_ClassName = "T_Test";
lObj = CreateObject(lStr_ClassName);

Class MainForm
{
    string mFileName;
    
    void OnButton_ReadDatabase()
    {
        T_DatabaseInfo lDatabaseInfo = new T_DatabaseInfo(mFileName);
        T_DBGoodsReader lDBGoodsReader = new T_DBGoodsReader;
        I_DBAdapter lDBAdapter = null;
        
        if lDatabaseInfo.DBType = Database.DBType1 then
            lDBAdapter = new T_DBAdapter1(mFileName);
        elseif lDatabaseInfo.DBType = Database.DBType2
            lDBAdapter = new T_DBAdapter2(mFileName);
        else
            // исключение "неизвестный тип БД
        endif
        
        lDBGoodsReader.SetAdapter(lAdapter);
        lDBGoodsReader.Init();
        lDBGoodsReader.Read();
        
        // показать на форме список товаров
    }
}

class Test
{
   string mFileName;
   File mFile;

   Test Set_FileName(pFileName)
   {
      Test res = *this;
      res.mFileName = pFileName;
      return res;
   }

   void Init ()
   {
      mFile = FileOpen(mFileName);
   }
   Test Init_Corrected ()
   {
      Test res = *this;
      res.mFile = FileOpen(mFileName);
      return res;
   }
   int Read(byte* dest, int count)
   {
      return FileRead(mFile, dest, count);
   }
};

int main() {
   Test t1 = Test().Set_FileName("foo.txt").Init(); // compile error: cannot convert expression of type 'void' to type 'Test'
   Test t2 = Test();
   Test t3 = Test().Set_FileName("foo.txt");
   Test t4 = Test().Set_FileName("foo.txt").Init_Corrected(); 
   byte* buffer = new byte[1024];
   t2.Read(buffer, 1024); // oops
   t3.Read(buffer, 1024); // oops
   t4.Read(buffer, 1024); // :)
}

Z>Class MainForm
Z>{
Z>    string mFileName;
    
Z>    void OnButton_ReadDatabase()
Z>    {
Z>        T_DatabaseInfo lDatabaseInfo = new T_DatabaseInfo(mFileName);
Z>        T_DBGoodsReader lDBGoodsReader = new T_DBGoodsReader;
Z>        I_DBAdapter lDBAdapter = null;
        
Z>        if lDatabaseInfo.DBType = Database.DBType1 then
Z>            lDBAdapter = new T_DBAdapter1(mFileName);
Z>        elseif lDatabaseInfo.DBType = Database.DBType2
Z>            lDBAdapter = new T_DBAdapter2(mFileName);
Z>        else
Z>            // исключение "неизвестный тип БД
Z>        endif
        
Z>        lDBGoodsReader.SetAdapter(lAdapter);
Z>        lDBGoodsReader.Init();
Z>        lDBGoodsReader.Read();
        
Z>        // показать на форме список товаров
Z>    }
Z>}
Z>

    public partial class Form1 : Form {
        Resolve di = new Resolve1();
        public Form1() {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e) {
            comboBox1.SelectedIndex = 0;
        }
        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {
            int num=comboBox1.SelectedIndex+1;
            di.GetConfig().SelectSource(num);
            update_goods();
        }
        void update_goods() {
            var reader=di.GetGoods();
            var lv = listView1;
            lv.BeginUpdate();
            lv.Items.Clear();
            Goods item;
            while(reader.Next(out item)) {
                var li = new ListViewItem();
                li.Text = item.name;
                li.SubItems.Add(String.Format("{0}", item.amount));
                li.SubItems.Add(String.Format("{0:F2}", item.price));
                lv.Items.Add(li);
            }
            lv.EndUpdate();
        }
    }

    class Goods {
        public string name = "";
        public double amount = 0;
        public double price = 0;
    };
    interface GoodsReader {
        bool Next(out Goods item);
    };
    interface Config {
        void SelectSource(int num);
    }
    interface Resolve {
        GoodsReader GetGoods();
        Config GetConfig();
    }

    class GoodsReader1 : GoodsReader {
        int index = 0;
        Goods[] list = new Goods[]{
            new Goods() { name="good1", amount=4, price=100 },
            new Goods() { name="good2", amount=2, price=150 },
            new Goods() { name="good3", amount=1, price= 75 }
        };
        public bool Next(out Goods item) {
            if (index < 0 || index >= list.Length) { item = null; return false; }
            item = list[index++];
            return true;
        }
    }
    class GoodsReader2 : GoodsReader {
        int index = 0;
        Goods[] list = new Goods[]{
            new Goods() { name="goodA", amount=40, price=120 },
            new Goods() { name="goodB", amount=12, price=130 },
            new Goods() { name="goodC", amount=11, price= 80 },
            new Goods() { name="goodE", amount= 1, price= 30 }
        };
        public bool Next(out Goods item) {
            if (index < 0 || index >= list.Length) { item = null; return false; }
            item = list[index++];
            return true;
        }
    }
    class Config1 : Config {
        Action<int> cb;
        public void SelectSource(int num) { if (cb != null) cb(num); }
        public Config1(Action<int> cb) { this.cb = cb; }
    }

    class Resolve1 : Resolve {
        int source = 1;
        public Config GetConfig() { return new Config1(num => source = num); }
        public GoodsReader GetGoods() {
            if (source == 1) return new GoodsReader1();
            if (source == 2) return new GoodsReader2();
            throw new Exception("invalid data source");
        }

    }

    partial class Form1 {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.IContainer components = null;

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param>
        protected override void Dispose(bool disposing) {
            if (disposing && (components != null)) {
                components.Dispose();
            }
            base.Dispose(disposing);
        }

        #region Windows Form Designer generated code

        /// <summary>
        /// Required method for Designer support - do not modify
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent() {
            this.comboBox1 = new System.Windows.Forms.ComboBox();
            this.listView1 = new System.Windows.Forms.ListView();
            this.ColName = new System.Windows.Forms.ColumnHeader();
            this.ColAmount = new System.Windows.Forms.ColumnHeader();
            this.ColPrice = new System.Windows.Forms.ColumnHeader();
            this.SuspendLayout();
            // 
            // comboBox1
            // 
            this.comboBox1.Anchor = ((System.Windows.Forms.AnchorStyles)(((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Left)
                        | System.Windows.Forms.AnchorStyles.Right)));
            this.comboBox1.FormattingEnabled = true;
            this.comboBox1.Items.AddRange(new object[] {
            "Source 1",
            "Source 2"});
            this.comboBox1.Location = new System.Drawing.Point(12, 12);
            this.comboBox1.Name = "comboBox1";
            this.comboBox1.Size = new System.Drawing.Size(260, 21);
            this.comboBox1.TabIndex = 0;
            this.comboBox1.SelectedIndexChanged += new System.EventHandler(this.comboBox1_SelectedIndexChanged);
            // 
            // listView1
            // 
            this.listView1.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom)
                        | System.Windows.Forms.AnchorStyles.Left)
                        | System.Windows.Forms.AnchorStyles.Right)));
            this.listView1.Columns.AddRange(new System.Windows.Forms.ColumnHeader[] {
            this.ColName,
            this.ColAmount,
            this.ColPrice});
            this.listView1.Location = new System.Drawing.Point(12, 48);
            this.listView1.Name = "listView1";
            this.listView1.Size = new System.Drawing.Size(260, 202);
            this.listView1.TabIndex = 1;
            this.listView1.UseCompatibleStateImageBehavior = false;
            this.listView1.View = System.Windows.Forms.View.Details;
            // 
            // ColName
            // 
            this.ColName.Text = "Name";
            // 
            // ColAmount
            // 
            this.ColAmount.Text = "Amount";
            // 
            // ColPrice
            // 
            this.ColPrice.Text = "Price";
            this.ColPrice.TextAlign = System.Windows.Forms.HorizontalAlignment.Right;
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.ClientSize = new System.Drawing.Size(284, 262);
            this.Controls.Add(this.listView1);
            this.Controls.Add(this.comboBox1);
            this.Name = "Form1";
            this.Text = "Form1";
            this.Load += new System.EventHandler(this.Form1_Load);
            this.ResumeLayout(false);

        }

        #endregion

        private System.Windows.Forms.ComboBox comboBox1;
        private System.Windows.Forms.ListView listView1;
        private System.Windows.Forms.ColumnHeader ColName;
        private System.Windows.Forms.ColumnHeader ColAmount;
        private System.Windows.Forms.ColumnHeader ColPrice;
    }

class Test
{
   string mFileName;
   File mFile;

   void Set_FileName (pFileName)
   {
      mFileName = pFileName;
   }

   void Init ()
   {
      mFile = FileOpen(mFileName);
   }
};

lTest = new Test;
lTest.Set_FileName("c:\test_file.txt")
lTest.Init();

public Form1 GetForm1() {
  var form=new Form1()
  form.di=this;
  // еще чего-нибудь подкручиваем
  return form;
}

   using(file=helper.OpenFile(filename)) {
     ...
   }

// global function
I_DBAdapter MakeDBAdapter(string pFileName) // 1
{
  I_DBAdapter lDBAdapter = null;
  T_DatabaseInfo lDatabaseInfo = new T_DatabaseInfo(pFileName);
  
  if lDatabaseInfo.DBType = Database.DBType1 then
    lDBAdapter = new T_DBAdapter1(pFileName);
  elseif lDatabaseInfo.DBType = Database.DBType2
    lDBAdapter = new T_DBAdapter2(pFileName);
  else
    // исключение "неизвестный тип БД
  endif
  
  return lDBAdapter;
}

// global function
T_DBGoodsReader MakeDBGoodsReader(string pFileName) // 2
{
  T_DBGoodsReader lDBGoodsReader = new T_DBGoodsReader;
  I_DBAdapter lDBAdapter = MakeDBAdapter(pFileName); // 1
  
  lDBGoodsReader.SetAdapter(lAdapter);
  lDBGoodsReader.Init();
  
  return lDBGoodsReader;
}

Class MainForm
{
  string mFileName;
  
  void OnButton_ReadDatabase()
  {
    T_DBGoodsReader lDBGoodsReader = MakeDBGoodsReader(mFileName); // 2
    
    lDBGoodsReader.Read();
    
    // показать на форме список товаров
  }
}

Z>Class MainForm
Z>{
Z>    string mFileName;
    
Z>    void OnButton_ReadDatabase()
Z>    {
Z>        T_DatabaseInfo lDatabaseInfo = new T_DatabaseInfo(mFileName);
Z>        T_DBGoodsReader lDBGoodsReader = new T_DBGoodsReader;
Z>        I_DBAdapter lDBAdapter = null;
        
Z>        if lDatabaseInfo.DBType = Database.DBType1 then
Z>            lDBAdapter = new T_DBAdapter1(mFileName);
Z>        elseif lDatabaseInfo.DBType = Database.DBType2
Z>            lDBAdapter = new T_DBAdapter2(mFileName);
Z>        else
Z>            // исключение "неизвестный тип БД
Z>        endif
        
Z>        lDBGoodsReader.SetAdapter(lAdapter);
Z>        lDBGoodsReader.Init();
Z>        lDBGoodsReader.Read();
        
Z>        // показать на форме список товаров
Z>    }
Z>}
Z>

SomeClass_make(int param1, string param2)
{
  SomeClass ret = new SomeClass;
  ret.Init(param1, param2);
  return ret;
}