internal static void ExplicitLoadingWithQuery(AdventureWorks adventureWorks)
{
ProductSubcategory subcategory = adventureWorks.ProductSubcategories.First(); // Execute query.
// SELECT TOP(1) [p].[ProductSubcategoryID], [p].[Name], [p].[ProductCategoryID]
// FROM [Production].[ProductSubcategory] AS [p]
subcategory.Name.WriteLine();
string categoryName = adventureWorks
.Entry(subcategory).Reference(entity => entity.ProductCategory)
.Query() // Return IQueryable<ProductCategory>.
.Select(category => category.Name).Single(); // Execute query.
// exec sp_executesql N'SELECT TOP(2) [e].[Name]
// FROM [Production].[ProductCategory] AS [e]
// WHERE [e].[ProductCategoryID] = @__get_Item_0',N'@__get_Item_0 int',@__get_Item_0=1
categoryName.WriteLine();
IQueryable <string> products = adventureWorks
.Entry(subcategory).Collection(entity => entity.Products)
.Query() // Return IQueryable<Product>.
.Select(product => product.Name); // Execute query.
// exec sp_executesql N'SELECT [e].[Name]
// FROM [Production].[Product] AS [e]
// WHERE [e].[ProductSubcategoryID] = @__get_Item_0',N'@__get_Item_0 int',@__get_Item_0=1
products.WriteLines();
}
internal static void ExplicitLoading(AdventureWorks adventureWorks)
{
ProductSubcategory subcategory = adventureWorks.ProductSubcategories.First(); // Execute query.
// SELECT TOP(1) [p].[ProductSubcategoryID], [p].[Name], [p].[ProductCategoryID]
// FROM [Production].[ProductSubcategory] AS [p]
subcategory.Name.WriteLine();
adventureWorks
.Entry(subcategory) // Return EntityEntry<ProductSubcategory>.
.Reference(entity => entity.ProductCategory) // Return ReferenceEntry<ProductSubcategory, ProductCategory>.
.Load(); // Execute query.
// exec sp_executesql N'SELECT [e].[ProductCategoryID], [e].[Name]
// FROM [Production].[ProductCategory] AS [e]
// WHERE [e].[ProductCategoryID] = @__get_Item_0',N'@__get_Item_0 int',@__get_Item_0=1
subcategory.ProductCategory.Name.WriteLine();
adventureWorks
.Entry(subcategory) // Return EntityEntry<ProductSubcategory>.
.Collection(entity => entity.Products) // Return CollectionEntry<ProductSubcategory, Product>.
.Load(); // Execute query.
// exec sp_executesql N'SELECT [e].[ProductID], [e].[ListPrice], [e].[Name], [e].[ProductSubcategoryID]
// FROM [Production].[Product] AS [e]
// WHERE [e].[ProductSubcategoryID] = @__get_Item_0',N'@__get_Item_0 int',@__get_Item_0=1
subcategory.Products.WriteLines(product => product.Name);
}
internal static void Default(AdventureWorks adventureWorks)
{
ProductCategory category = adventureWorks.ProductCategories.First();
category.Name = "Update"; // Valid value.g
ProductSubcategory subcategory = adventureWorks.ProductSubcategories.First();
subcategory.ProductCategoryID = -1; // Invalid value.
try
{
adventureWorks.SaveChanges();
}
catch (DbUpdateException exception)
{
exception.WriteLine();
// Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while updating the entries. See the inner exception for details.
// ---> System.Data.SqlClient.SqlException: The UPDATE statement conflicted with the FOREIGN KEY constraint "FK_ProductSubcategory_ProductCategory_ProductCategoryID". The conflict occurred in database "AdventureWorks", table "Production.ProductCategory", column 'ProductCategoryID'. The statement has been terminated.
adventureWorks.Entry(category).Reload();
category.Name.WriteLine(); // Accessories
adventureWorks.Entry(subcategory).Reload();
subcategory.ProductCategoryID.WriteLine(); // 1
}
}
