在通用方法内将未知参数添加到Func [英] Add unknown parameter to a Func inside a generic method

问题描述

我在网上查看了许多资源，但我认为这是不可能的，或者我是从错误的角度进行研究的.

I have looked at many resources online but I think this is something not possible or I am approaching it from the wrong angle.

我正在从子表中生成ID列表，并确定父表中的外键ID是否包含在子ID列表中.例如j =>！ids.Contains(j.InvestorId).下面的代码将无法编译，因为whereFilter无法接受参数，但是您可以看到我想要的效果.

I am generating a list of ids from a child table and determining if the foreign key id in the parent table contains in the list of child ids. e.g. j => !ids.Contains(j.InvestorId). The code below will not compile as whereFilter can not take a parameter but you can see the effect I would like.

希望有一种方法可以代替预先获取id并将附加参数传递给whereFilter.

Hopefully, there is a way instead of getting the ids beforehand and passing in an additional parameter to whereFilter.

public List<int> ValidateReferentialIntegrity<TChild, TParent>(string childFilePath, 
    string parentFilePath, 
    Func<TParent, int, bool> whereFilter, 
    Func<TParent, int> selector) 
{
    var childList = ReadCsvFile<TChild>(typeof(TChild).Name, childFilePath);
    var parentList = ReadCsvFile<TParent>(typeof(TParent).Name, parentFilePath);

    var ids = childList.Select(s => (int)s.GetId()).ToList();
    var unidentifiableIds = parentList.Where(whereFilter(ids))
        .Select(selector).ToList();
    return unidentifiableIds;
}

推荐答案

public List<int> ValidateReferentialIntegrity<TChild, TParent>(string childFilePath, 
    string parentFilePath, 
    Func<TParent, IList<int>, bool> whereFilter,  // <- change #1 is here, IList<int>
    Func<TParent, int> selector) 
{
    var childList = ReadCsvFile<TChild>(typeof(TChild).Name, childFilePath);
    var parentList = ReadCsvFile<TParent>(typeof(TParent).Name, parentFilePath);

    var ids = childList.Select(s => (int)s.GetId()).ToList();
    var unidentifiableIds = parentList
        .Where(p => whereFilter(p, ids))    // <- change #2 is here, pass object to whereFilter
        .Select(selector)
        .ToList();
    return unidentifiableIds;
}

并这样称呼它:

var list = ValidateReferentialIntegrity<TChild, TParent>(
    "file1.csv", 
    "file2.csv", 
    (TParent parent, IList<int> childIds) => childIds.Contains(parent.InvestorId),
    parent => parent.InvestorId);

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