Question

如何为多个表创建Generic方法？我的桌子：

客户
员工

我需要使用Generic Method搜索它们。我尝试了以下内容：

呼叫：

var predicateSearchCustomer = GetSearchPredicate<Customer>(search,Types.Customer);
var predicateSearchEmployee = GetSearchPredicate<Employee>(search,Types.Employee);

我的方法：

public Expression<Func<T, bool>> GetSearchPredicate<T>(string parametrs, Types Types)
{
    var predicateInner = PredicateBuilder.False<T>();

    var paramertsForSearch = new List<string>(parametrs.Split(' '));

    paramertsForSearch.RemoveAll(string.IsNullOrEmpty);

        foreach (var item in paramertsForSearch)
        {
            var itemSearch = item;
            switch (Types)
            {
                case Types.Customer:

                    predicateInner = predicateInner.Or(x => x.CustomerName.Contains(itemSearch));
                    predicateInner = predicateInner.Or(x => x.CustomerFamily.Contains(itemSearch));
                    break;
                case Types.Employee:
                    predicateInner = predicateInner.Or(x => x.EmployeeName.Contains(itemSearch));
                    predicateInner = predicateInner.Or(x => x.EmployeeFamily.Contains(itemSearch));
                    break;
            }

        }


    return predicateInner;
}

错误：

错误5'T'不包含'CustomerName'的定义，不包含扩展方法'CustomerName'接受'T'类型的第一个参数可以找到（你错过了使用指令或程序集引用？）

如何将T转换为Customer或Employee？

Answer 1

如果必须根据传递给泛型方法的类型编写switch语句来执行不同的操作，那么您的方法不是通用的。所以写两种方法。代码将更易于阅读（并将编译为额外的奖励）。

话虽如此，你的方法可以改写成通用的：

public Expression<Func<T, bool>> GetSearchPredicate<T>(string parameters,
                                                       Func<T, string, bool> test1,
                                                       Func<T, string, bool> test2)
{
    var predicateInner = PredicateBuilder.False<T>();
    var paramertsForSearch = new List<string>(parametrs.Split(' '));

    paramertsForSearch.RemoveAll(string.IsNullOrEmpty);

    foreach (var item in paramertsForSearch)
    {
        var itemSearch = item;
        predicateInner = predicateInner.Or(x => test1(x, itemSearch));
        predicateInner = predicateInner.Or(x => test2(x, itemSearch));
    }

    return predicateInner;
}

var predicateSearchCustomer = 
    GetSearchPredicate<Customer>(search,
                                 (cust, term) => cust.CustomerName.Contains(term),
                                 (cust, term) => cust.CustomerFamily.Contains(term));

var predicateSearchEmployee = 
    GetSearchPredicate<Employee>(search,
                                 (empl, term) => empl.EmployeeName.Contains(term),
                                 (cust, term) => empl.EmployeeFamily.Contains(term));

使用多个表的通用方法搜索数据

1 个答案: