Expression<Func<T,TResult>>和Func<T,TResult>

//使用LambdaExpression构建表达式树
            Expression<Func<int, int, int, int>> expr = (x, y, z) => (x + y) / z;
            Console.WriteLine(expr.Compile()(1, 2, 3));

  string mid = ",middle part,";
            ///匿名写法
            Func<string, string> anonDel = delegate(string param)
            {
                param += mid;
                param += " And this was added to the string.";
                return param;
            };
            ///λ表达式写法
            Func<string, string> lambda = param =>
                {
                    param += mid;
                    param += " And this was added to the string.";
                    return param;
                };
            ///λ表达式写法(整形)
            Func<int, int> lambdaint = paramint =>
                {
                    paramint = 5;
                    return paramint;
                };
            ///λ表达式带有两个参数的写法
            Func<int, int, int> twoParams = (x, y) =>
                {
                  return  x*y;
                };
            MessageBox.Show("匿名方法："+anonDel("Start of string"));
            MessageBox.Show("λ表达式写法:" + lambda("Lambda expression"));
            MessageBox.Show("λ表达式写法(整形):" + lambdaint(4).ToString());
            MessageBox.Show("λ表达式带有两个参数:" + twoParams(10, 20).ToString());

    public static class DynamicLinqExpressions
     {
 
         public static Expression<Func<T, bool>> True<T>() { return f => true; }
         public static Expression<Func<T, bool>> False<T>() { return f => false; }
 
         public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
                                                             Expression<Func<T, bool>> expr2)
         {
             var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
             return Expression.Lambda<Func<T, bool>>
                   (Expression.Or(expr1.Body, invokedExpr), expr1.Parameters);
         }
 
         public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                                                              Expression<Func<T, bool>> expr2)
         {
             var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
             return Expression.Lambda<Func<T, bool>>
                   (Expression.And(expr1.Body, invokedExpr), expr1.Parameters);
         }
 
     }

       public static IEnumerable<T> FilterBy<T>(this IEnumerable<T> collection, IEnumerable<KeyValuePair<string, string>> query)
         {
             var filtersCount = int.Parse(query.SingleOrDefault(k => k.Key.Contains("filterscount")).Value);
             
             Expression<Func<T, bool>> finalquery = null;
 
             for (var i = 0; i < filtersCount; i += 1)
             {
                 var filterValue = query.SingleOrDefault(k => k.Key.Contains("filtervalue" + i)).Value;
                 var filterCondition = query.SingleOrDefault(k => k.Key.Contains("filtercondition" + i)).Value;
                 var filterDataField = query.SingleOrDefault(k => k.Key.Contains("filterdatafield" + i)).Value;
                 var filterOperator = query.SingleOrDefault(k => k.Key.Contains("filteroperator" + i)).Value;
 
                 Expression<Func<T, bool>> current = n => GetQueryCondition(n, filterCondition, filterDataField, filterValue);
 
                 if (finalquery == null)
                 {
                     finalquery = current;
                 }
                 else if (filterOperator == "1")
                 {
                     finalquery = finalquery.Or(current);
                 }
                 else
                 {
                     finalquery = finalquery.And(current);
                 }
             };
 
             if (finalquery != null)
                 collection = collection.AsQueryable().Where(finalquery);
 
             return collection;
         }