根据asp.net mvc3中的下拉列表数据获取列表

Question

我的模块中有两个下拉列表.

在一个下拉列表中,我已经硬编码了所有运算符 <,>,<=,>=,==

在第二个下拉列表中,我有像员工一样的硬编码员工 1000,2000,3000,4000....50000

现在,如果我<从一个列表和2000第二个列表中选择并单击"提交"按钮,我应该获得薪水低于2000的员工列表.

我想在asp.net mvc3中这样做

我怎样才能完成这项任务？我需要为此编写存储过程吗？

我创建了下拉列表,如:

viewModel.OperatorsList = new[]
{
  new SelectListItem { Value = "<", Text = "<" },
  new SelectListItem { Value = ">", Text = ">" },  
  new SelectListItem { Value = "<=", Text = "<=" },
  new SelectListItem { Value = ">=", Text = ">=" },
  new SelectListItem { Value = "==", Text = "==" }
};

viewModel.SalaryList = new[]
{
  new SelectListItem { Value = "1000", Text = "1000" },
  new SelectListItem { Value = "2000", Text = "2000" },  
  new SelectListItem { Value = "3000", Text = "3000" },

  // and so on
};

我用它来显示视图中的下拉列表:

<%: Html.DropDownListFor(x => x.Operators, Model.OperatorsList)%>

Answer 1

好吧,你可以做那样的事情

假设viewModel是......你的viewModel,你Employee有一个有财产的实体Salary(int在这个样本中,它可能是decimal在现实世界中)

创建一个静态助手类

public static class MyHelper
    {
        // a dictionary for your operators and corresponding ExpressionType
        public static Dictionary<string, ExpressionType> ExpressionTypeDictionary = new Dictionary<string, ExpressionType>
        {
            {"<", ExpressionType.LessThan},
            {">", ExpressionType.GreaterThan},
            {">=", ExpressionType.GreaterThanOrEqual}
            //etc
        };
        //a method to filter your queryable
        public static IQueryable<Employee> FilterSalary(this IQueryable<Employee> queryable, int salary, string operatorType)
        {
            //left part of the expression : m
            var parameter = Expression.Parameter(typeof(Employee), "m");
            //body is the right part of the expression : m
            Expression body = parameter;
            //m.Salary
            body = Expression.Property(body, "Salary");
            //m.Salary <= 1000 (for example)
            body = Expression.MakeBinary(ExpressionTypeDictionary[operatorType], body, Expression.Constant(salary));
            //m => m.Salary <=1000
            var lambda = Expression.Lambda<Func<Employee, bool>>(body, new[] { parameter });
            //so it will be queryable.Where(m => m.Salary <= 1000)
            return queryable.Where(lambda);
        }
}

用法

var queryable = context.All<Employee>();//or something like that, returning an IQueryable<Employee>
queryable = queryable.FilterSalary(viewModel.Salary, viewModel.Operators);