# 表達式樹

表達式樹是不可變的數據結構， 只能換新樹

``` public static void Main()
{
Expression<Func<int, int>> addFive = num => num + 5;
{
var parameter = lambdaExp.Parameters.First();
Console.WriteLine(parameter.Name);
Console.WriteLine(parameter.Type);

Console.WriteLine(lambdaExp.Parameters.Last().Name); //跟上面同一個
Console.WriteLine(lambdaExp.Parameters.Last().Type);
}
}```

```public static void Main()
{
// 常量表達式樹
ConstantExpression one = Expression.Constant(1, typeof(int));
ConstantExpression two = Expression.Constant(2, typeof(int));
// 二進位表達式樹
}```

ExpressionType:（ConvertChecked 和Convert明明c#寫法一樣，怎麼表達不同節點類型，迷茫... Multiply和MultiplyChecked，迷茫...，NewArrayBounds 多維數組）  ```//
// 摘要:
//     An addition operation, such as a + b, without overflow checking, for numeric
//     operands.
//
// 摘要:
//     An addition operation, such as (a + b), with overflow checking, for numeric operands.
//
// 摘要:
//     A bitwise or logical AND operation, such as (a & b) in C# and (a And b) in Visual
//     Basic.
And = 2,
//
// 摘要:
//     A conditional AND operation that evaluates the second operand only if the first
//     operand evaluates to true. It corresponds to (a && b) in C# and (a AndAlso b)
//     in Visual Basic.
AndAlso = 3,
//
// 摘要:
//     An operation that obtains the length of a one-dimensional array, such as array.Length.
ArrayLength = 4,
//
// 摘要:
//     An indexing operation in a one-dimensional array, such as array[index] in C#
//     or array(index) in Visual Basic.
ArrayIndex = 5,
//
// 摘要:
//     A method call, such as in the obj.sampleMethod() expression.
Call = 6,
//
// 摘要:
//     A node that represents a null coalescing operation, such as (a ?? b) in C# or
//     If(a, b) in Visual Basic.
Coalesce = 7,
//
// 摘要:
//     A conditional operation, such as a > b ? a : b in C# or If(a > b, a, b) in Visual
//     Basic.
Conditional = 8,
//
// 摘要:
//     A constant value.
Constant = 9,
//
// 摘要:
//     A cast or conversion operation, such as (SampleType)obj in C#or CType(obj, SampleType)
//     in Visual Basic. For a numeric conversion, if the converted value is too large
//     for the destination type, no exception is thrown.
Convert = 10,
//
// 摘要:
//     A cast or conversion operation, such as (SampleType)obj in C#or CType(obj, SampleType)
//     in Visual Basic. For a numeric conversion, if the converted value does not fit
//     the destination type, an exception is thrown.
ConvertChecked = 11,```
View Code  ```//
// 摘要:
//     A division operation, such as (a / b), for numeric operands.
Divide = 12,
//
// 摘要:
//     A node that represents an equality comparison, such as (a == b) in C# or (a =
//     b) in Visual Basic.
Equal = 13,
//
// 摘要:
//     A bitwise or logical XOR operation, such as (a ^ b) in C# or (a Xor b) in Visual
//     Basic.
ExclusiveOr = 14,
//
// 摘要:
//     A "greater than" comparison, such as (a > b).
GreaterThan = 15,
//
// 摘要:
//     A "greater than or equal to" comparison, such as (a >= b).
GreaterThanOrEqual = 16,
//
// 摘要:
//     An operation that invokes a delegate or lambda expression, such as sampleDelegate.Invoke().
Invoke = 17,
//
// 摘要:
//     A lambda expression, such as a => a + a in C# or Function(a) a + a in Visual
//     Basic.
Lambda = 18,
//
// 摘要:
//     A bitwise left-shift operation, such as (a << b).
LeftShift = 19,
//
// 摘要:
//     A "less than" comparison, such as (a < b).
LessThan = 20,
//
// 摘要:
//     A "less than or equal to" comparison, such as (a <= b).
LessThanOrEqual = 21,
//
// 摘要:
//     An operation that creates a new System.Collections.IEnumerable object and initializes
//     it from a list of elements, such as new List<SampleType>(){ a, b, c } in C# or
//     Dim sampleList = { a, b, c } in Visual Basic.
ListInit = 22,
//
// 摘要:
//     An operation that reads from a field or property, such as obj.SampleProperty.
MemberAccess = 23,
//
// 摘要:
//     An operation that creates a new object and initializes one or more of its members,
//     such as new Point { X = 1, Y = 2 } in C# or New Point With {.X = 1, .Y = 2} in
//     Visual Basic.
MemberInit = 24,```
View Code  ``` //
// 摘要:
//     An arithmetic remainder operation, such as (a % b) in C# or (a Mod b) in Visual
//     Basic.
Modulo = 25,
//
// 摘要:
//     A multiplication operation, such as (a * b), without overflow checking, for numeric
//     operands.
Multiply = 26,
//
// 摘要:
//     An multiplication operation, such as (a * b), that has overflow checking, for
//     numeric operands.
MultiplyChecked = 27,
//
// 摘要:
//     An arithmetic negation operation, such as (-a). The object a should not be modified
//     in place.
Negate = 28,
//
// 摘要:
//     A unary plus operation, such as (+a). The result of a predefined unary plus operation
//     is the value of the operand, but user-defined implementations might have unusual
//     results.
UnaryPlus = 29,
//
// 摘要:
//     An arithmetic negation operation, such as (-a), that has overflow checking. The
//     object a should not be modified in place.
NegateChecked = 30,
//
// 摘要:
//     An operation that calls a constructor to create a new object, such as new SampleType().
New = 31,
//
// 摘要:
//     An operation that creates a new one-dimensional array and initializes it from
//     a list of elements, such as new SampleType[]{a, b, c} in C# or New SampleType(){a,
//     b, c} in Visual Basic.
NewArrayInit = 32,
//
// 摘要:
//     An operation that creates a new array, in which the bounds for each dimension
//     are specified, such as new SampleType[dim1, dim2] in C# or New SampleType(dim1,
//     dim2) in Visual Basic.
NewArrayBounds = 33,
//
// 摘要:
//     A bitwise complement or logical negation operation. In C#, it is equivalent to
//     (~a) for integral types and to (!a) for Boolean values. In Visual Basic, it is
//     equivalent to (Not a). The object a should not be modified in place.
Not = 34,```
View Code

（Quote節點類型是什麼？）  ``` //
// 摘要:
//     A bitwise complement or logical negation operation. In C#, it is equivalent to
//     (~a) for integral types and to (!a) for Boolean values. In Visual Basic, it is
//     equivalent to (Not a). The object a should not be modified in place.
Not = 34,
//
// 摘要:
//     An inequality comparison, such as (a != b) in C# or (a <> b) in Visual Basic.
NotEqual = 35,
//
// 摘要:
//     A bitwise or logical OR operation, such as (a | b) in C# or (a Or b) in Visual
//     Basic.
Or = 36,
//
// 摘要:
//     A short-circuiting conditional OR operation, such as (a || b) in C# or (a OrElse
//     b) in Visual Basic.
OrElse = 37,
//
// 摘要:
//     A reference to a parameter or variable that is defined in the context of the
Parameter = 38,
//
// 摘要:
//     A mathematical operation that raises a number to a power, such as (a ^ b) in
//     Visual Basic.
Power = 39,
//
// 摘要:
//     An expression that has a constant value of type System.Linq.Expressions.Expression.
//     A System.Linq.Expressions.ExpressionType.Quote node can contain references to
//     parameters that are defined in the context of the expression it represents.
Quote = 40,
//
// 摘要:
//     A bitwise right-shift operation, such as (a >> b).
RightShift = 41,```
View Code

Expression：BinaryExpression、IndexExpression、MethodCallExpression、UnaryExpression、BlockExpression、GotoExpression、DynamicExpression、LambdaExpression、MemberExpression等。

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