如何在 QueryAsync 中使用现成的 Func<> 委托？

Question

我有一个问题，我的方法中有相同的 Func。我是单独拿出来的，但现在的问题是如何给它传参数。我想在几个地方使用它，但是我不知道如何从QueryAsync方法中获取必要的参数

我的 func 委托

private Func<Authors, AuthorInPrintingEditions, PrintingEditions, Authors> _relationDelegate =
        (Authors authors, AuthorInPrintingEditions relation, PrintingEditions printingEdition) =>
        {
            if (!_dictionaryResult.ContainsKey(authors.Id))
            {
                _dictionaryResult.Add(authors.Id, new Authors()
                {
                    Id = authors.Id,
                    Name = authors.Name,
                    AuthorInPrintingEditions = printingEdition == null
                        ? new List<AuthorInPrintingEditions>()
                        : new List<AuthorInPrintingEditions>()
                        {
                            new AuthorInPrintingEditions()
                            {
                                PrintingEdition = printingEdition
                            }
                        }
                });
            }
            else
            {
                if (printingEdition != null)
                {
                    _dictionaryResult[authors.Id].AuthorInPrintingEditions.Add(new AuthorInPrintingEditions()
                    {
                        PrintingEdition = printingEdition
                    });
                }
            }

            return authors;
        };

我的方法，当我想用​​的时候

        using (var conneсtion = CreateConnection())
        {
            await conneсtion.QueryAsync<Authors, AuthorInPrintingEditions, PrintingEditions, Authors>(query,
                (authors, authorInPrintingEditions, printingEdition), <--- in this row I want use delegate
                new { skip = skip, pageSize = pageSize }, splitOn: "Id,AuthorId,Id");

            return _dictionaryResult.Values.ToList();
        }

不明白怎么给它传参数，一般情况下是否可行，还是复制粘贴会比较容易

Answer 1

如果您希望重用委托并且还能够使用参数， 尝试使用这样的东西：

public class AuthorsMapper
{
    public int Parameter1;
    public string Parameter2;

    public Func<Authors, AuthorInPrintingEditions, PrintingEditions, Authors> Map =>
    // Your existing code that can now use parameters
}

并像这样使用它：

var mapper = new AuthorsMapper 
{
    Parameter1 = 742,
    Parameter2 = "House"
};

await conneсtion.QueryAsync<Authors, AuthorInPrintingEditions, PrintingEditions, Authors>
    (query, mapper.Map, ...);