public static void Show()
{
{
Expression <Func <int, int, int> > exp = (x, y) => x * y + 2;
// 此时需求更改，需要将 x*y + 2 变成 x*y -2， 首先需要解析上面的expression 需要用到ExpressionVisitor类
OperationVisitor visitor = new OperationVisitor();
Expression expNew = visitor.Modify(exp);
}
{
Expression <Func <int, int, int> > exp1 = (m, n) => m * n + 2 + 3 + Get(m);
OperationVisitor visitor = new OperationVisitor();
Expression expNew = visitor.Modify(exp1);
}
{
//用处
{
var source = new List <People>().AsQueryable();
var result = source?.Where <People>(p => p.Age > 5); // Select * from People Where Age > 5
Expression <Func <People, bool> > lambda = x => x.Age > 5;
ConditionBuilderVisitor visitor = new ConditionBuilderVisitor();
visitor.Visit(lambda);
Console.WriteLine(visitor.Condition());
}
{
Expression <Func <People, bool> > lambda = x => x.Age > 5 &&
x.Id > 5 &&
x.Name.StartsWith("I") &&
x.Name.EndsWith("n") &&
x.Name.Contains("n");
var sql = string.Format("Delete from [{0}] where {1}", nameof(People), " [Age] > 5 AND [ID] > 5");
ConditionBuilderVisitor visitor = new ConditionBuilderVisitor();
visitor.Visit(lambda);
Console.WriteLine(visitor.Condition());
}
}
}
