For what purposes in the Object Sender, Eventargs

using system;
Using System.Collections.Genic;
Using System.comPonentModel;
Using System.Data;
Using System.Drawing;
Using System.Linq;
Using System.Text;
using system.threading.tasks;
using System.Windows.Forms;
using system.data.sqlclient;
Namespace CBS.ADO_NET.TableConstraints.
{
  Public Partial Class Form1: Form
  {
    Public Form1 ()
    {
      Initializecomponent ();
    }
    Private Void Form1_Load (Object Sender, Eventargs E)
    {
      String ConnectionString = @ "data source =. \ sqlexpress; initial catalog = shopdb; Integrated Security = True;"; // Creating a connection string
      Dataset ds = new dataset ();
      DataTable Customers = New Datatable ("Customers");
      Datatable Orders = New Datatable ("Orders");
      Using (SQLConnection Connection = New Sqlconnection (ConnectionString))
      {
        Connection.open ();
        SQLommand Customerscmd = New Sqlcommand ("Select Customerno, Lname, Fname, Address1, Phone From Customers", Connection);
        SQLommand Orderscmd = New Sqlcommand ("Select Order), Customerno, OrderDate From Orders", Connection);
        SqldataReader OrdersReader = Orderscmd.executeReader (); // Get a DataReader for the OrderDetails table
        // LoadWithSchema method allows you to create a DataTable object based on the DataReader object
        // With the restrictions for columns as in the database and fill this table data
        Orders.LoadWithschema (OrdersReader);
        Ordersreader.Close ();
        SQLDATAREADER CUSTOMERSRADER = Customerscmd.executeReader ();
        Customers.LoadWithschema (CustomersReader);
        CustomersReader.Close ();
      }
      // The DataReader object does not have information about the limitations of Datatable objects, such as
      // UniqueConstraint, ForeignKeyConstraint and PrimaryKey, so you will have to create them manually
      customers.primaryKey = new datacolumn [] {customers.columns [0]};
      ds.Tables.Addrange (New Datatable [] {Customers, Orders});
      // Creating ForeignKeyConstraint Restriction for OrderDetails table
      var fk_customersorders = new foreignkeyconstraint (customers.columns ["Customerno"], orders.columns ["Customerno"]);
      Orders.constraints.add (fk_customersorders);
      parentgridview.datasource = customers; // Linking the ParentGridView controls element with table Products
      childdatagridview.datasource = orders; // Binding the ChilddatagRidView controls with the OrderDetails table
    }
  }
}

using system;
Using System.Collections.Genic;
Using System.Linq;
using system.threading.tasks;
using System.Windows.Forms;
Namespace CBS.ADO_NET.TableConstraints.
{
  Static Class Program
  {
    /// & LT; Summary & GT;
    /// The Main Entry Point for the Application.
    /// & LT; / Summary & GT;
    [Stathed]
    Static Void Main ()
    {
      Application.enablevisualstyles ();
      Application.SetCompatibleTextRenderingDefault (False);
      Application.Run (New Form1 ());
    }
  }
}

using system;
Using System.Collections.Genic;
Using System.Linq;
Using System.Text;
using system.threading.tasks;
using system.data.sqlclient;
Using System.Data;
Namespace CBS.ADO_NET.TableConstraints.
{
  Static Class TBaleExtensoinclass.
  {
    // This method writes data to a table based on DataReader
    Public Static Void Loadwithschema (This Datatable Table, SqldataReader Reader)
    {
      table.createschemaFromReader (Reader);
      Table.load (Reader); // Load Method is used to download the DataTable rows from the data source in the DataTable table.
    } 
// This method creates restrictions on columns table based on the resulting DataReader object.
    Private Static Void CreateschemaFromReader (This Datatable Table, SqldataReader Reader)
    {
      DataTable Schematable = Reader.getSchematable (); // Method Returns the table Describing the SQLDATAREADER object column metadata.
      Foreach (Datarow SchemaRow in Schematable.Rows)
      {
        DataColumn Column = New DataColumn ((String) SchemaRow ["columnname"]); // Creating a column with a column name in the data source
        column.allowdbnull = (bool) SchemaRow ["AllowDBNULL"]; // Obtaining the value of the property AllowDBNULL
        column.datatype = (type) SCHEMAROW ["DATATYPE"]; // Get the value of the Datatype property
        column.unique = (BOOL) SCHEMAROW ["ISUNIQUE"]; // Get the value of the Unique Properties
        column.Readonly = (BOOL) SCHEMAROW ["ISReadOnly"]; // Obtaining the value of the Readonly Properties
        column.autoincrement = (BOOL) SCHEMAROW ["ISIIDENTIY"]; // Receive the value of the AutoInCrement property
        if (column.datatype == typeof (string)) // If the String type field
          column.maxlength = (int) SchemaRow ["columnsize"]; // Get the value of the MaxLength property
        if (column.autoincrement == true) // if the field with auto-accord
        {column.autoincrementstep = -1; column.autoincrementseed = 0; } // Set AutoIncrementStep and AutoIncrementSeed properties
        table.columns.add (column); // Add Created Column to Columns Collection Tables
      }
    }
  }
}

Answer 1, Authority 100%

This is the so-called event handlers

form1_load (Object Sender, Eventargs E)

Sender is the so-called call context, or an object that caused this event.
E are used to transmit parameters to call the method.
Eventargs – Basic class for classes with data on events.

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