如何使用dapper将多对多关系映射到列表

Question

I have a class AnalysisRule

public class AnalysisRule
{
    public long Id { get; set; }
    public Analysis Analysis { get; set; }
    public AnalysisCategory AnalysisCategory { get; set; }
    public Gender Gender { get; set; }
    public bool FatherHerdBookRequired { get; set; }
    public bool MotherHerdBookRequired { get; set; }
    public List<Breed> AllowedBreeds { get; set; }
}

That has a list of Breeds

public class Breed
{
    public long BreedId { get; set; }
    public long AnimalTypeId { get; set; }
    public long BreedCode { get; set; }
    public string BreedName { get; set; }
    public string BreedAcronym { get; set; }
}

This is a many to many relationship that I bind together with a DB table AnalysisRulesBreeds

Breeds

And AnalysisRules

With Dapper I have tried

    var sql = @"select *
                from ""AnalysisRules"" 
                join ""AnalysisCategory"" on ""AnalysisRules"".""AnalysisCategoryId"" = ""AnalysisCategory"".""Id""  
                join ""Analysis"" on ""AnalysisRules"".""AnalysisId"" = ""Analysis"".""Id""
                left join ""AnalysisRulesBreeds"" on ""AnalysisRulesBreeds"".""AnalysisRuleId"" = ""AnalysisRules"".""Id""
                left join ""Breed"" on ""AnalysisRulesBreeds"".""BreedId"" = ""Breed"".""BreedId""
                where ""AnalysisId"" = :AnalysisId";
    rules = sqlConnection.QueryAsync<AnalysisRule, AnalysisCategory, Analysis, Breed, AnalysisRule>(
        sql,
        (ar, c, a, b) =>
        {
            ar.AnalysisCategory = c;
            ar.Analysis = a;
            ar.Breeds.Add(b);
            return ar;
        },
        new
        {
            AnalysisId = analysisId
        },
        splitOn:"BreedId");

Which gives me

´When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id Parameter name: splitOn

If I run the same query in SQL Developer I get 2 rows out with same Id but with different data in Breed, so the query should be good enough.

So how do I get these 2 rows into one AnalysisRule entity where Breeds consist of 2 Breed entities?

EDIT I now have

                    sqlConnection.Open();

                var sql = @"select  ar.*,
                                    ac.*,
                                    b.*                 

                            from ""AnalysisRules"" ar
                            join ""AnalysisCategory"" ac on ar.""AnalysisCategoryId"" = ac.""Id""  
                            join ""Analysis"" a on ar.""AnalysisId"" = a.""Id""

                            left join ""AnalysisRulesBreeds""  on ""AnalysisRulesBreeds"".""AnalysisRuleId"" = ar.""Id""
                            left join ""Breed"" b  on ""AnalysisRulesBreeds"".""BreedId"" = b.""Id""

                            where ""AnalysisId"" = :AnalysisId";

                var rules = sqlConnection.QueryAsync<AnalysisRule, AnalysisCategory, Analysis, Breed, AnalysisRule>(
                    sql,
                    (ar, c, a, b) =>
                    {
                        ar.AnalysisCategory = c;
                        ar.Analysis = a;
                        ar.Breeds.Add(b);
                        return ar;
                    },
                    new
                    {
                        AnalysisId = analysisId
                    });

                return await rules;

Removed the splitOn, changed AnalysisRulesBreedsId to Id but I still get

When using the multi-mapping APIs ensure you set the splitOn param if you have keys other than Id Parameter name: splitOn

If I do the same query in SQLDev I get

Answer 1

By selecting * you get the columns of every joined table. Also you set splitOn to BreedId . Now Dapper expects that to separate the row columns of one joined table from the next, it should look for a column named BreedId .

This does not work because all tables except AnalysisRulesBreeds use Id as id column name.

Try removing the splitOn parameter, then it will default to Id . Then adjust your select-clause to only select from the tables you actually need in the result, eg.

select AnalysisRule.*, AnalysisCategory.*, Analysis.*, Breed.*

(assuming that your Analysis table and AnalysisCategory table follow the convention of having an Id column named ´Id´).