列表未添加 C# 中的所有值

我尝试了下面的代码来创建 json 代码，代码工作正常。

我从数据库加载值，但只有最后一个值我得到了输出。剩余值未添加。

DataTable dt = new DataTable();
var objectToSerialize = new RootObject();
SqlConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["dbconnection"].ToString());
SqlCommand command = new SqlCommand("select * from IFlicksMenu", connection);
SqlDataAdapter da = new SqlDataAdapter(command);
da.Fill(dt);

foreach (DataRow dr in dt.Rows)
{
    foreach (DataColumn col in dt.Columns)
    { 
        objectToSerialize.contacts = new List<Cont> 
        {
            new Cont
            { 
                sno = dr["Cinema"].ToString(), 
                name = dr["Gallery"].ToString(), 
                address =  dr["star"].ToString(), 
                gender =  dr["video"].ToString(), 
                em = dr["em"].ToString(),
                phone=new Phone { mobile=dr["phonone"].ToString() } 
            },
        };          
    }

    JavaScriptSerializer serializer = new JavaScriptSerializer();
    Response.Write(serializer.Serialize(new { item = objectToSerialize.contacts }));
}

输出是

{
    "item":[
         {
        "phone":{
            "mobile":"99528748474"
                },
        "sno":"ACTRESS",
        "name":"ACTRESS",
        "em":"scd",
        "address":"ACTRESS",
        "gender":"TRAILER"
        }
    ]
}

您正在实例化里面的列表foreach对于每次迭代，因此需要最后一次迭代。您可以在外部定义 List 对象foreach以及里面的价值观foreach

List<Cont> ContCollection =  new List<Cont>();
foreach (DataRow dr in dt.Rows)
{
    foreach (DataColumn col in dt.Columns)
    { 
        ContCollection.Add(new Cont(){
                            sno = dr["Cinema"].ToString(), 
                            name = dr["Gallery"].ToString(), 
                            address =  dr["star"].ToString(), 
                            gender =  dr["video"].ToString(), 
                            em = dr["em"].ToString(),
                            phone=new Phone { mobile=dr["phonone"].ToString() }
                           });


    }
    objectToSerialize.contacts = ContCollection;
    JavaScriptSerializer serializer = new JavaScriptSerializer();
    Response.Write(serializer.Serialize(new { item = objectToSerialize.contacts }));
}