因此上述代码中的Where和Select分别接受了一个Expression Tree作为参数。最后的query对象中包含了整个序列每个操作对应的表达式树,QueryProvider就可以通过分析表达式树,翻译成SQL或者直接进行查询动作了。 这种用法有点类似于解释器模式。你可以用Expression Tree来表示一种逻辑,然后解析它来驱动你的业务逻辑。原本属于具体语言...
IQueryable <T>有一个Expression类型的属性叫做Expression,当使用Linq To SQL执行Linq查询时会调用那些扩展方法,而扩展方法都要求一个Expression<T>类型的参数,扩展方法接收这个作为参数的表达式树后将它作为IQueryable <T>集合的Expression属性来使用,IQueryable<T>还有一个叫做IQueryProvider...
Visual Studio 2008的samples包含一个叫ExpressionTreeVisualizer的程序。它可以用来呈现表达式树。图1你可以看到一个展示上面简单表达式语句的对话框截图。注意,对话框上面部分显示的是lambda表达式,下面是用TreeView控件显示的其组成部分。 图1:VS2008 C# Samples中的ExpressionTreeVisualizer创建一个表达式树的象征性的输出 ...
1 public class SqlExpressionTree 2 { 3 public string GetQuerySql<T>(Expression<Func<T, bool>> condi) 4 { 5 string condition = "select * from "+typeof(T).Name+" "+ typeof(T).Name + " where "; 6 Bi 蓝夏 2022/03/10
You create expression trees in your code. You build the tree by creating each node and attaching the nodes into a tree structure. You learn how to create expressions in the article on building expression trees.Expression trees are immutable. If you want to modify an expression tree, you must...
You can have the C# or Visual Basic compiler create an expression tree for you based on an anonymous lambda expression, or you can create expression trees manually by using theSystem.Linq.Expressionsnamespace. When a lambda expression is assigned to a variable of typeExpression<TDelegate>, the...
You can have the C# or Visual Basic compiler create an expression tree for you based on an anonymous lambda expression, or you can create expression trees manually by using theSystem.Linq.Expressionsnamespace. When a lambda expression is assigned to a variable of typeExpression<TDelegate>, the...
You can have the C# or Visual Basic compiler create an expression tree for you based on an anonymous lambda expression, or you can create expression trees manually by using theSystem.Linq.Expressionsnamespace. When a lambda expression is assigned to a variable of typeExpression<TDelegate>, the...
SqlExpression.cs An expression that represents a scalar value or a SQL token in a SQL tree. This type is typically used by database providers (and other extensions). It is generally not used in application code. C# [System.Diagnostics.DebuggerDisplay("{Microsoft.EntityFrameworkCore.Query.Expr...
.NET Framework4.5版本Expression表达式转换为SQL语句,支持SqlServer、MySql、Oracle、Sqlite、PostgreSql;基于Dapper实现了不同数据库对应的数据仓储Repository; - zqlovejyc/SQLBuilder