Expression Tree Tutorial IfThen
The Expression.IfThen method creates a ConditionalExpression that represents a conditional block with an if statement. For example, you have the following code.
int num = 60; if(num > 10) { Console.WriteLine("num is greater than 10"); }
Here is the code that is required to build the same functionality using expression tree.
int num = 60; var testCondition = Expression.Constant(num > 10); var ifTrueBlock = WriteLineExpression("num is greater than 10"); var ifThenExpr = Expression.IfThen(testCondition, ifTrueBlock); Expression.Lambda<Action>(ifThenExpr).Compile()();
This example shows how to create an expression that represents an if block. Here is the code for WriteLineExpression method
public static Expression WriteLineExpression(string s) { return Expression.Call(null, typeof(Console).GetMethod("WriteLine", new Type[] { typeof(String) }), Expression.Constant(s)); }