Initial commit

vs4win/Chapter10/WorkingWithEFCore/Program.Modifications.cs

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+using Microsoft.EntityFrameworkCore.ChangeTracking; // EntityEntry<T>
+using Microsoft.EntityFrameworkCore.Storage; // IDbContextTransaction
+using Packt.Shared;
+
+partial class Program
+{
+  static void ListProducts(int? productIdToHighlight = null)
+  {
+    using (Northwind db = new())
+    {
+      if ((db.Products is null) || (db.Products.Count() == 0))
+      {
+        Fail("There are no products.");
+        return;
+      }
+
+      WriteLine("| {0,-3} | {1,-35} | {2,8} | {3,5} | {4} |",
+        "Id", "Product Name", "Cost", "Stock", "Disc.");
+
+      foreach (Product p in db.Products)
+      {
+        ConsoleColor previousColor = ForegroundColor;
+
+        if (productIdToHighlight == p.ProductId)
+        {
+          ForegroundColor = ConsoleColor.Green;
+        }
+
+        WriteLine("| {0:000} | {1,-35} | {2,8:$#,##0.00} | {3,5} | {4} |",
+          p.ProductId, p.ProductName, p.Cost, p.Stock, p.Discontinued);
+
+        ForegroundColor = previousColor;
+      }
+    }
+  }
+
+  static (int affected, int productId) AddProduct(
+    int categoryId, string productName, decimal? price)
+  {
+    using (Northwind db = new())
+    {
+      Product p = new()
+      {
+        CategoryId = categoryId,
+        ProductName = productName,
+        Cost = price,
+        Stock = 72
+      };
+
+      // set product as added in change tracking
+      EntityEntry<Product> entity = db.Products.Add(p);
+      WriteLine($"State: {entity.State}, ProductId: {p.ProductId}");
+
+      // save tracked change to database
+      int affected = db.SaveChanges();
+      WriteLine($"State: {entity.State}, ProductId: {p.ProductId}");
+
+      return (affected, p.ProductId);
+    }
+  }
+
+  static (int affected, int productId) IncreaseProductPrice(
+    string productNameStartsWith, decimal amount)
+  {
+    using (Northwind db = new())
+    {
+      // get first product whose name starts with name
+      Product updateProduct = db.Products.First(
+        p => p.ProductName.StartsWith(productNameStartsWith));
+
+      updateProduct.Cost += amount;
+
+      int affected = db.SaveChanges();
+
+      return (affected, updateProduct.ProductId);
+    }
+  }
+
+  static int DeleteProducts(string productNameStartsWith)
+  {
+    using (Northwind db = new())
+    {
+      using (IDbContextTransaction t = db.Database.BeginTransaction())
+      {
+        WriteLine("Transaction isolation level: {0}",
+          arg0: t.GetDbTransaction().IsolationLevel);
+
+        IQueryable<Product>? products = db.Products?.Where(
+        p => p.ProductName.StartsWith(productNameStartsWith));
+
+        if (products is null)
+        {
+          WriteLine("No products found to delete.");
+          return 0;
+        }
+        else
+        {
+          db.Products.RemoveRange(products);
+        }
+
+        int affected = db.SaveChanges();
+        t.Commit();
+        return affected;
+      }
+    }
+  }
+}