c# - 动态 linq :Creating an extension method that produces JSON result

Question

我一直在尝试创建一个返回 JSON 格式字符串的动态 linq 扩展方法 - 我正在使用 System.Linq.Dynamic 和 Newtonsoft.Json，但我无法让 Linq.Dynamic 解析“cell=new object[]”部分。也许太复杂了？有任何想法吗？ :

我的主要方法:

static void Main(string[] args)
{
    NorthwindDataContext db = new NorthwindDataContext();
    var query = db.Customers;
    string json = JSonify<Customer>
                    .GetJsonTable(
                        query, 
                        2, 
                        10, 
                        "CustomerID"
                        , 
                        new string[] 
                            { 
                                "CustomerID", 
                                "CompanyName", 
                                "City", 
                                "Country", 
                                "Orders.Count"
                            });
    Console.WriteLine(json);
}

JSonify 类

public static class JSonify<T>
{
    public static string GetJsonTable(
        this IQueryable<T> query, 
        int pageNumber, 
        int pageSize, 
        string IDColumnName, 
        string[] columnNames)
    {
        string selectItems =
            String.Format(@"
                        new
                        {
                            {{0}} as ID,
                            cell = new object[]{{{1}}}
                        }", 
                          IDColumnName, 
                          String.Join(",", columnNames));

        var items = new
        {
            page = pageNumber,
            total = query.Count(),
            rows =
                query
                    .Select(selectItems)
                    .Skip(pageNumber * pageSize)
                    .Take(pageSize)
        };

        return JavaScriptConvert.SerializeObject(items);
        // Should produce this result:
        // {
        //    "page":2,
        //    "total":91,
        //    "rows":
        //        [
        //        {"ID":"FAMIA","cell":["FAMIA","Familia Arquibaldo","Sao Paulo","Brazil",7]},
        //        {"ID":"FISSA","cell":["FISSA","FISSA Fabrica Inter. Salchichas S.A.","Madrid","Spain",0]},
        //        {"ID":"FOLIG","cell":["FOLIG","Folies gourmandes","Lille","France",5]},
        //        {"ID":"FOLKO","cell":["FOLKO","Folk och fä HB","Bräcke","Sweden",19]},
        //        {"ID":"FRANK","cell":["FRANK","Frankenversand","München","Germany",15]},
        //        {"ID":"FRANR","cell":["FRANR","France restauration","Nantes","France",3]},
        //        {"ID":"FRANS","cell":["FRANS","Franchi S.p.A.","Torino","Italy",6]},
        //        {"ID":"FURIB","cell":["FURIB","Furia Bacalhau e Frutos do Mar","Lisboa","Portugal",8]},
        //        {"ID":"GALED","cell":["GALED","Galería del gastrónomo","Barcelona","Spain",5]},
        //        {"ID":"GODOS","cell":["GODOS","Godos Cocina Típica","Sevilla","Spain",10]}
        //        ]
        // }

    }

}

Answer 1

这真的很难看，字符串替换可能存在一些问题，但它产生了预期的结果:

public static class JSonify
{
    public static string GetJsonTable<T>(
        this IQueryable<T> query, int pageNumber, int pageSize, string IDColumnName, string[] columnNames)
    {
        string select = string.Format("new ({0} as ID, \"CELLSTART\" as CELLSTART, {1}, \"CELLEND\" as CELLEND)", IDColumnName, string.Join(",", columnNames));
        var items = new
        {
            page = pageNumber,
            total = query.Count(),
            rows = query.Select(select).Skip((pageNumber - 1) * pageSize).Take(pageSize)
        };
        string json = JavaScriptConvert.SerializeObject(items);
        json = json.Replace("\"CELLSTART\":\"CELLSTART\",", "\"cell\":[");
        json = json.Replace(",\"CELLEND\":\"CELLEND\"", "]");
        foreach (string column in columnNames)
        {
            json = json.Replace("\"" + column + "\":", "");
        }
        return json;
    }
}