C#實現通用資料過濾表單

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/// <summary> /// 擷取查詢運算式樹 (zuowenjun.cn) /// </summary> /// <typeparam name="TEntity"></typeparam> /// <param name="fieldName"></param> /// <param name="operatorName"></param> /// <param name="value"></param> /// <param name="value2"></param> /// <returns></returns> public  static  Expression<Func<TEntity,  bool >> GetQueryExpression<TEntity>( string  fieldName,  string  operatorName,  string  value,  string  value2)  where  TEntity :  class {      PropertyInfo fieldInfo =  typeof (TEntity).GetProperty(fieldName, BindingFlags.Instance | BindingFlags.Public | BindingFlags.IgnoreCase);      Type pType = fieldInfo.PropertyType;      if  ( string .IsNullOrEmpty(operatorName))      {          throw  new  ArgumentException( "運算子不可為空！" ,  "operatorName" );      }      dynamic convertedValue;      if  (!value.TryChangeType(pType,  out  convertedValue))      {          throw  new  ArgumentException( string .Format( "【{0}】的查詢實值型別不正確,必須為{1}類型！" , General.GetDisplayName(fieldInfo), pType.FullName),  "value" );      }      ParameterExpression expParameter = Expression.Parameter( typeof (TEntity),  "f" );      MemberExpression expl = Expression.Property(expParameter, fieldInfo);      ConstantExpression expr = Expression.Constant(convertedValue, pType);      Expression expBody =  null ;      Type expType =  typeof (Expression);      var  expMethod = expType.GetMethod(operatorName,  new [] { expType, expType });      if  (expMethod !=  null )      {          expBody = (Expression)expMethod.Invoke( null ,  new  object [] { expl, expr });      }      else  if  (FilterOperators.Between == operatorName)      {          dynamic convertedValue2;          if  (!value2.TryChangeType(pType,  out  convertedValue2))          {              throw  new  ArgumentException( string .Format( "【{0}】的查詢值2類型不正確,必須為{1}類型！" , General.GetDisplayName(fieldInfo), pType.FullName),  "value" );          }          ConstantExpression expr2 = Expression.Constant(convertedValue2, pType);          expBody = Expression.GreaterThanOrEqual(expl, expr);          expBody = Expression.AndAlso(expBody, Expression.LessThanOrEqual(expl, expr2));      }      else  if  ( new [] { FilterOperators.Contains, FilterOperators.StartsWith, FilterOperators.EndsWith }.Contains(operatorName))      {          expBody = Expression.Call(expl,  typeof ( string ).GetMethod(operatorName,  new  Type[] {  typeof ( string ) }), expr);      }      else      {          throw  new  ArgumentException( "無效的運算子！" ,  "operatorName" );      }      Expression<Func<TEntity,  bool >> lamExp = Expression.Lambda<Func<TEntity,  bool >>(expBody, expParameter);      return  lamExp; }

C#實現通用資料過濾表單