Is it possible to repeat in the <dynamic> list?

Question

In the past few days, I have been trying to find a way to iterate over a List<dynamic> without much success.

What am I doing:

 while (dr.Read()) { dynamic e = new ExpandoObject(); var d = e as IDictionary<string, object>; for (var i = 0; i < dr.FieldCount; i++) d.Add(dr.GetName(i), DBNull.Value.Equals(dr[i]) ? null : dr[i]); result.Add(e); } 

the above code is a method that returns an IEnumerable<dynamic> , and then in my controller I return the data with:

 dynamic irionErrorsExport = oracleDbManager.GetStrCtrlNDGWithErrors(tableName, queryParamsList, periodo, "", "", ""); 

and now I'm stuck, since I need to iterate over irionErrorsExport and create a “concrete” object / s for use with EPPlus.

Can someone tell me if this is possible and give a simple example?

Answer 1

Yes, you can iterate over a dynamic object:

 dynamic source = new List<int>() {1, 2, 3, 4, 5, 6}; foreach (var item in source) { Console.Write(item.ToString()); } 

Prints 123456 in the console.

However, this will result in a runtime exception if iteration is not possible:

Consider the following code:

 dynamic source = 2; foreach (var item in source) { Console.Write(item.ToString()); } 

RuntimeBinderException :

Cannot implicitly convert type 'int' to 'System.Collections.IEnumerable'

Edit : You should know the differences between foreach for regular variables and dynamic . They are explained in another SO question: C # 4.0 'dynamic' and foreach statement

Answer 2

 while (dr.Read()) { IDictionary<string, object> e = new ExpandoObject(); for (var i = 0; i < dr.FieldCount; i++) e.Add(dr.GetName(i), DBNull.Value.Equals(dr[i]) ? null : dr[i]); result.Add(e); } 

From the calling method, you “cheat”. You know that your dynamic collection is an ExpandoObject , so

 foreach (IDictionary<string, object> row in result) { foreach (var kv in row) { Console.WriteLine("{0}: {1}", kv.Key, kv.Value); } } 

In the end, it is better if your method simply returns List<IDictionary<string, object>> , no dynamic .

Reflection of dynamic types is difficult. If you can’t use duck print (duck print is when you know that an object can duck Duck() , even if you don’t know what it is, so you can do dynamic x = something; x.Duck(); ) then it will only be semi-solid. If you do not trust me, you can try to read. How can I reflect the elements of a dynamic object?

Answer 3

If you fill out a DataTable as here , you can use Json.Net and easily get a specific object

 //Sample DataTable DataTable dt = new DataTable(); dt.Columns.Add("IntCol"); dt.Columns.Add("StrCol"); dt.Rows.Add(new object[]{1,"1"}); dt.Rows.Add(new object[]{2,"2"}); var jsonstr = JsonConvert.SerializeObject(dt); var list = JsonConvert.DeserializeObject<List<YourClass>>(jsonstr); public class YourClass { public int IntCol { set; get; } public string StrCol { set; get; } }