问题
Question:
Given to object FooBar that contains a List of Bar, with FooBar and Bar define as such:
class FooBar{
int FooID {get;set;}
string FooProperty1 {get;set;}
List<Bar> Bars {get;set;};
}
class Bar{
int BarID {get;set;}
string BarProperty1 {get;set;}
string BarProperty2 {get;set;}
string BarProperty3 {get;set;}
}
I get the following CSV as input:
1,FooProperty1,BarID_1,BarProperty1_1,BarProperty2_1,BarProperty3_1,BarID_2,BarProperty1_2,BarProperty2_2,BarProperty3_2
Where the field BarID, BarProperty1, BarProperty2, BarProperty3 are suffixed by their indice in the collection.
How do I deserialise this input into my object?
input Exemple:
1 instance of FooBar, and 2 sub Bar: 1,FooProperty1,BarID_1,BarProperty1_1,BarProperty2_1,BarProperty3_1,BarID_2,BarProperty1_2,BarProperty2_2,BarProperty3_2
1 instance of FooBar but no Bar:1,FooProperty1
Tries:
I have try using Convert in order to map those property to a new instance of Bar like :
public class FooBarMap : ClassMap<FooBar>
{
public FooBarMap()
{
Map(m => m.FooID);
Map(m => m.Bars).ConvertUsing(row =>
{
var list = new List<Bar>
{
new Bar {
BarProperty1 = row.GetField("BarProperty1_1"),
BarProperty2 = row.GetField("BarProperty2_1"),
// .. Other Properties
},
new Bar {}, //.. Same on _2
};
return list;
});
}
}
Of course no control over the input. I would have been sending Json/Xml not CSV.
回答1:
Its possible with a custom type converter but tricky.
You need to decorate the property with an Index attribute (even though it's not used)
public class FooBar
{
[Index(2)]
public List<Bar> Bars { get; set; }
}
The converter is used for both reading and writing, so you need to override two methods:
public class BarListConverter : DefaultTypeConverter
{
public override object ConvertFromString(string text, IReaderRow row, MemberMapData memberMapData)
{
var list = new List<Bar>();
if (text == null) return list;
do
{
var barIndex = list.Count + 1;
var bar = new Bar
{
BarID = row.GetField<int>($"BarID_{barIndex}"),
BarProperty1 = row.GetField<string>($"BarProperty1_{barIndex}"),
BarProperty2 = row.GetField<string>($"BarProperty2_{barIndex}"),
BarProperty3 = row.GetField<string>($"BarProperty3_{barIndex}")
};
list.Add(bar);
} while (row.Context.CurrentIndex > 0 && row.Context.CurrentIndex < row.Context.Record.Length - 1);
return list;
}
public override string ConvertToString(object value, IWriterRow row, MemberMapData memberMapData)
{
var bars = value as List<Bar>;
if (bars == null) return null;
foreach (var bar in bars)
{
row.WriteField(bar.BarID);
row.WriteField(bar.BarProperty1);
row.WriteField(bar.BarProperty2);
row.WriteField(bar.BarProperty3);
}
return null;
}
}
}
Reading:
public List<FooBar> Reading()
{
using (var stream = new MemoryStream())
using (var writer = new StreamWriter(stream))
using (var reader = new StreamReader(stream))
using (var csv = new CsvReader(reader))
{
writer.WriteLine(
"FooID,FooProperty1,BarID_1,BarProperty1_1,BarProperty2_1,BarProperty3_1,BarID_2,BarProperty1_2,BarProperty2_2,BarProperty3_2");
writer.WriteLine("1,Foo1,1,2,3,4,5,6,7,8");
writer.Flush();
stream.Position = 0;
csv.Configuration.HeaderValidated = null;
csv.Configuration.MissingFieldFound = null;
csv.Configuration.TypeConverterCache.AddConverter<List<Bar>>(new BarListConverter());
return csv.GetRecords<FooBar>().ToList();
}
}
Writing:
public string Writing(List<FooBar> data)
{
using (var stream = new MemoryStream())
using (var writer = new StreamWriter(stream))
using (var reader = new StreamReader(stream))
using (var csv = new CsvWriter(writer))
{
csv.Configuration.HasHeaderRecord = false;
csv.Configuration.TypeConverterCache.AddConverter<List<Bar>>(new BarListConverter());
csv.WriteRecords(data);
writer.Flush();
stream.Position = 0;
return reader.ReadToEnd();
}
回答2:
I have made a very simplified method that will iterate over the key/value pairs...
private static FooBar Parse(string value)
{
// a basic check for null or empty string
if (String.IsNullOrEmpty(value)) throw new ArgumentNullException(nameof(value));
// split the string
string[] split = value.Split(',');
// a basic check for properly formed key/value pairs in the string
if (split.Length < 2 || split.Length % 2 != 0)
throw new ArgumentException("Malformed string.", nameof(value));
// put the values into our object
var result = new FooBar();
// Foo pair
result.FooID = Int32.Parse(split[0]);
result.FooProperty1 = split[1];
// Bar pairs
result.Bars = new List<Bar>();
for (int i = 2; i < split.Length; i = i + 4)
{
result.Bars.Add(new Bar()
{
BarID = split[i],
BarProperty1 = split[i+1],
BarProperty2 = split[i+2],
BarProperty3 = split[i+3]
});
}
return result;
}
I ran this against the two examples like so
string value = "1,FooProperty1";
FooBar result = Parse(value); // works
and
string value = "1,FooProperty1,BarID_1,BarProperty1_1,BarProperty2_1,BarProperty3_1,BarID_2,BarProperty1_2,BarProperty2_2,BarProperty3_2";
FooBar result = Parse(value); // works
note that your class needs to be slightly updated to
public class FooBar
{
public int FooID { get; set; }
public string FooProperty1 { get; set; }
public List<Bar> Bars { get; set; }
}
public class Bar
{
public string BarID { get; set; } // you originally had this as int
public string BarProperty1 { get; set; }
public string BarProperty2 { get; set; }
public string BarProperty3 { get; set; }
}
To me, this option seems far less convoluted and, easier to read overall. I don't particularly see any reason that you have to force the conversion to be done via other means such as using the CSVHelper class.
来源：https://stackoverflow.com/questions/55745715/using-csvhelper-how-to-deserialise-an-csv-with-a-list-of-sub-item