■ 객체 리스트를 필터링하는 방법을 보여준다.
▶ 객체 리스트 필터링 하기 예제 (C#)
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using System; using System.Collections.Generic; using System.Linq; List<Student> studentList = new List<Student> { new Student { Name = "강동구", Age = 70 }, new Student { Name = "강남구", Age = 60 }, new Student { Name = "강서구", Age = 50 }, new Student { Name = "홍길동", Age = 20 }, new Student { Name = "김철수", Age = 40 }, new Student { Name = "김영희", Age = 30 } }; List<Filter> filterList = new List<Filter> { new Filter { PropertyName = "Name", OperationType = OperationType.StartsWith , Value = "강" }, new Filter { PropertyName = "Age" , OperationType = OperationType.GreaterThan, Value = 50 } }; var expression = ExpressionBuilder.GetExpression<Student>(filterList).Compile(); var result = studentList.Where(expression); foreach(Student student in result) { Console.WriteLine(student.Name); } |
▶ OperationType.cs
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namespace TestProject { /// <summary> /// 연산 타입 /// </summary> public enum OperationType { /// <summary> /// 작다. /// </summary> LessThan, /// <summary> /// 작거나 같다. /// </summary> LessThanOrEqual, /// <summary> /// 같다. /// </summary> Equals, /// <summary> /// 크거나 같다. /// </summary> GreaterThanOrEqual, /// <summary> /// 크다. /// </summary> GreaterThan, /// <summary> /// 포함한다. /// </summary> Contains, /// <summary> /// 시작한다. /// </summary> StartsWith, /// <summary> /// 끝난다. /// </summary> EndsWith } } |
▶ Filter.cs
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namespace TestProject { /// <summary> /// 필터 /// </summary> public class Filter { //////////////////////////////////////////////////////////////////////////////////////////////////// Property ////////////////////////////////////////////////////////////////////////////////////////// Public #region 속성명 - PropertyName /// <summary> /// 속성명 /// </summary> public string PropertyName { get; set; } #endregion #region 연산 타입 - OperationType /// <summary> /// 연산 타입 /// </summary> public OperationType OperationType { get; set; } #endregion #region 값 - Value /// <summary> /// 값 /// </summary> public object Value { get; set; } #endregion } } |
▶ ExpressionBuilder.cs
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using System; using System.Collections.Generic; using System.Linq.Expressions; using System.Reflection; namespace TestProject { /// <summary> /// 수식 빌더 /// </summary> public static class ExpressionBuilder { //////////////////////////////////////////////////////////////////////////////////////////////////// Field ////////////////////////////////////////////////////////////////////////////////////////// Static //////////////////////////////////////////////////////////////////////////////// Private #region Field /// <summary> /// Contains 메소드 정보 /// </summary> private static MethodInfo _containsMethodInfo = typeof(string).GetMethod("Contains"); /// <summary> /// StartsWith 메소드 정보 /// </summary> private static MethodInfo _startsWithMethodInfo = typeof(string).GetMethod("StartsWith", new Type[] { typeof(string) }); /// <summary> /// EndsWith 메소드 정보 /// </summary> private static MethodInfo _endsWithMethodInfo = typeof(string).GetMethod("EndsWith", new Type[] { typeof(string) }); #endregion //////////////////////////////////////////////////////////////////////////////////////////////////// Method ////////////////////////////////////////////////////////////////////////////////////////// Static //////////////////////////////////////////////////////////////////////////////// Public #region 수식 구하기 - GetExpression<T>(filterList) /// <summary> /// 수식 구하기 /// </summary> /// <typeparam name="T">타입</typeparam> /// <param name="filterList">필터 리스트</param> /// <returns>수식</returns> public static Expression<Func<T, bool>> GetExpression<T>(IList<Filter> filterList) { if(filterList == null || filterList.Count == 0) { return null; } ParameterExpression parameterExpression = Expression.Parameter(typeof(T), "t"); Expression expression = null; if(filterList.Count == 1) { expression = GetExpression<T>(parameterExpression, filterList[0]); } else if(filterList.Count == 2) { expression = GetExpression<T>(parameterExpression, filterList[0], filterList[1]); } else { while(filterList.Count > 0) { Filter filter1 = filterList[0]; Filter filter2 = filterList[1]; if(expression == null) { expression = GetExpression<T>(parameterExpression, filterList[0], filterList[1]); } else { expression = Expression.AndAlso(expression, GetExpression<T>(parameterExpression, filterList[0], filterList[1])); } filterList.Remove(filter1); filterList.Remove(filter2); if(filterList.Count == 1) { expression = Expression.AndAlso(expression, GetExpression<T>(parameterExpression, filterList[0])); filterList.RemoveAt(0); } } } return Expression.Lambda<Func<T, bool>>(expression, parameterExpression); } #endregion //////////////////////////////////////////////////////////////////////////////// Private #region 수식 구하기 - GetExpression<T>(parameterExpression, filter) /// <summary> /// 수식 구하기 /// </summary> /// <typeparam name="T">타입</typeparam> /// <param name="parameterExpression">파라미터 수식</param> /// <param name="filter">필터</param> /// <returns>수식</returns> private static Expression GetExpression<T>(ParameterExpression parameterExpression, Filter filter) { MemberExpression memberExpression = Expression.Property(parameterExpression, filter.PropertyName); ConstantExpression constantExpression = Expression.Constant(filter.Value); switch(filter.OperationType) { case OperationType.LessThan : return Expression.LessThan (memberExpression, constantExpression); case OperationType.LessThanOrEqual : return Expression.LessThanOrEqual (memberExpression, constantExpression); case OperationType.Equals : return Expression.Equal (memberExpression, constantExpression); case OperationType.GreaterThanOrEqual : return Expression.GreaterThanOrEqual(memberExpression, constantExpression); case OperationType.GreaterThan : return Expression.GreaterThan (memberExpression, constantExpression); case OperationType.Contains : return Expression.Call(memberExpression, _containsMethodInfo , constantExpression); case OperationType.StartsWith : return Expression.Call(memberExpression, _startsWithMethodInfo, constantExpression); case OperationType.EndsWith : return Expression.Call(memberExpression, _endsWithMethodInfo , constantExpression); } return null; } #endregion #region 수식 구하기 - GetExpression<T>(parameterExpression, filter1, filter2) /// <summary> /// 수식 구하기 /// </summary> /// <typeparam name="T">타입</typeparam> /// <param name="parameterExpression">파라미터 수식</param> /// <param name="filter1">필터 1</param> /// <param name="filter2">필터 2</param> /// <returns>수식</returns> private static BinaryExpression GetExpression<T>(ParameterExpression parameterExpression, Filter filter1, Filter filter2) { Expression expression1 = GetExpression<T>(parameterExpression, filter1); Expression expression2 = GetExpression<T>(parameterExpression, filter2); return Expression.AndAlso(expression1, expression2); } #endregion } } |