1. 查詢全部字段

using (NorthwindContext context = new NorthwindContext()) {var expr = context.Products;foreach (var item in expr){Console.WriteLine(item.ProductName);} } SELECT [Extent1].[ProductID] AS [ProductID], [Extent1].[CategoryID] AS [CategoryID], [Extent1].[ProductName] AS [ProductName], [Extent1].[UnitPrice] AS [UnitPrice], [Extent1].[Discontinued] AS [Discontinued]FROM [dbo].[Product] AS [Extent1]

2. 查詢指定字段

var expr = context.Products.Select(p => new { p.ProductID, p.ProductName }); var expr = from p in context.Productsselect new { 商品ID = p.ProductID, 商品名稱 = p.ProductName };

　　上述兩種形式所生成的SQL是一樣的。

SELECT [Extent1].[ProductID] AS [ProductID], [Extent1].[ProductName] AS [ProductName]FROM [dbo].[Product] AS [Extent1]

3. First/FirstOrDefault

var expr = context.Products.First(); SELECT TOP (1) [c].[ProductID] AS [ProductID], [c].[CategoryID] AS [CategoryID], [c].[ProductName] AS [ProductName], [c].[UnitPrice] AS [UnitPrice], [c].[Discontinued] AS [Discontinued]FROM [dbo].[Product] AS [c]

4. Single/SingleOrDefault

var expr = context.Products.SingleOrDefault(p => p.ProductID == 1); SELECT TOP (2) [Extent1].[ProductID] AS [ProductID], [Extent1].[CategoryID] AS [CategoryID], [Extent1].[ProductName] AS [ProductName], [Extent1].[UnitPrice] AS [UnitPrice], [Extent1].[Discontinued] AS [Discontinued]FROM [dbo].[Product] AS [Extent1]WHERE 1 = [Extent1].[ProductID]

轉載于:https://www.cnblogs.com/libingql/p/4047609.html

總結

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