Expression trees represent code in a tree-like data structure where each node is an expression. This enables dynamic modification of executable code, execution of LINQ queries in various databases, and creation of dynamic queries. Expression trees can be compiled into executable code using the Expression<TDelegate>.Compile() method.

1. Expression Tree
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2. Expression tree
Expression trees represent code in a tree-like data structure, where each node is
an expression.
This enables dynamic modification of executable code, the execution of LINQ
queries in various databases, and the creation of dynamic queries.

3. Lambda
Statement lambda
(x, y) => { return x + y; }
Expression lambda
(x, y) => x + y

4. Lambda Expression
Using the System.Linq.Expressions namespace
Expression<Func<int, bool>> expr = n => n > 5;

5. Expression<TDelegate>.Compile
Compile the expression tree into executable code.
Expression<Func<int, bool>> expr = n => n > 5;
Func<int, bool> deleg = expr.Compile();
deleg(3);

6. Expression<Func<int, bool>>
n => n > 5
Body : BinaryExpression
n > 5
Left : Expression
n
Right : Expression
5
NodeType : ExpressionType
GreaterThan
NodeType : ExpressionType
Lambda
ReturnType : Type
Boolean

7. ParameterExpression
ParameterExpression iParam =
Expression.Parameter(typeof(int), "n");
>
n 5
λ

8. BinaryExpression
BinaryExpression binaryExpr =
Expression.GreaterThan(iParam, constantExpr);
>
n 5
λ

9. ConstantExpression
ConstantExpression constantExpr =
Expression.Constant(5, typeof(int));
>
n 5
λ

10. LambdaExpression
Expression<Func<int, bool>> expr =
Expression.Lambda<Func<int, bool>>(binaryExpr, iParam);
>
n 5
λ

11. Reference
Expression Tree - MSDN
https://msdn.microsoft.com/en-us/library/bb397951.aspx