asp.net-mvc-3 – 根据asp.net mvc3中的下拉列表数据获取列表

我的模块中有两个下拉列表.

在一个下拉列表中,我对所有运算符进行了硬编码,例如<,>,< =,> =,==

在第二个下拉列表中,我有员工的硬编码,如1000,2000,3000,4000 …. 50000

现在如果我选择<从一个列表和2000从第二个列表中单击提交按钮我应该得到薪水低于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)%>

解决方法

假设viewModel是…你的viewModel,并且你有一个具有属性Salary的实体Employee(此示例中为int,它在现实世界中可能是小数)

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);

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