How to Create Relationship in SDF

First, you need to create the database and tables with the necessary relationships. For example, let's assume you have two tables: Customers and Orders.

CREATE TABLE Customers (
    CustomerID INT PRIMARY KEY,
    Name NVARCHAR(100) NOT NULL
);

CREATE TABLE Orders (
    OrderID INT PRIMARY KEY,
    CustomerID INT,
    OrderDate DATETIME,
    FOREIGN KEY (CustomerID) REFERENCES Customers(CustomerID)
);

Insert some sample data into the tables:

INSERT INTO Customers (CustomerID, Name) VALUES (1, 'John Doe');
INSERT INTO Customers (CustomerID, Name) VALUES (2, 'Jane Smith');

INSERT INTO Orders (OrderID, CustomerID, OrderDate) VALUES (101, 1, '2023-10-01');
INSERT INTO Orders (OrderID, CustomerID, OrderDate) VALUES (102, 2, '2023-10-02');

In your Windows Forms application, you need to connect to the SDF database using the SqlCeConnection class.
 

using System;
using System.Data.SqlServerCe;
using System.Windows.Forms;

public partial class Form1 : Form
{
    private string connectionString = @"Data Source=your_database.sdf;";

    public Form1()
    {
        InitializeComponent();
        LoadData();
    }

    private void LoadData()
    {
        using (SqlCeConnection connection = new SqlCeConnection(connectionString))
        {
            connection.Open();
            string query = @"
                SELECT Customers.Name, Orders.OrderID, Orders.OrderDate
                FROM Customers
                INNER JOIN Orders ON Customers.CustomerID = Orders.CustomerID
                WHERE Customers.CustomerID = @CustomerID";

            using (SqlCeCommand command = new SqlCeCommand(query, connection))
            {
                command.Parameters.AddWithValue("@CustomerID", 1); // Example CustomerID

                using (SqlCeDataReader reader = command.ExecuteReader())
                {
                    if (reader.Read())
                    {
                        lblCustomerName.Text = reader["Name"].ToString();
                        lblOrderID.Text = reader["OrderID"].ToString();
                        lblOrderDate.Text = reader["OrderDate"].ToString();
                    }
                }
            }
        }
    }
}

In your Windows Forms designer, add labels to display the data:

- lblCustomerName
- lblOrderID
- lblOrderDate

When you run the application, it will fetch the data from the related tables (Customers and Orders) and display it in the labels on the form.