[英]Converting Complex types of C# into YAML
我是YAML的初學者,正在研究如何將YAML解析為C#。 在這里,我試圖解析C#Object模塊,其中我有C#中的DataTable類或Type類等復雜對象類型的數據。 我知道如何使用YAMLDotNet庫轉換基本類型,但實際上不知道如何對這些類型進行相同的操作。 請幫忙。
DataTable
是一個丟失屬性的復雜對象。 最簡單的方法是將與您相關的數據提取到更簡單的數據結構中,然后將其序列化。 但是,如果您確實需要,可以創建自定義IYamlTypeConverter
。 下面是一個示例,它將序列化表的列名和類型,以及行的值:
public class DataTableTypeConverter : IYamlTypeConverter
{
public bool Accepts(Type type)
{
return typeof(DataTable).IsAssignableFrom(type);
}
public object ReadYaml(IParser parser, Type type)
{
var table = new DataTable();
parser.Expect<MappingStart>();
ReadColumns(parser, table);
ReadRows(parser, table);
parser.Expect<MappingEnd>();
return table;
}
private static void ReadColumns(IParser parser, DataTable table)
{
var columns = parser.Expect<Scalar>();
if (columns.Value != "columns")
{
throw new YamlException(columns.Start, columns.End,
"Expected a scalar named 'columns'");
}
parser.Expect<MappingStart>();
while (parser.Allow<MappingEnd>() == null)
{
var columnName = parser.Expect<Scalar>();
var typeName = parser.Expect<Scalar>();
table.Columns.Add(columnName.Value, Type.GetType(typeName.Value));
}
}
private static void ReadRows(IParser parser, DataTable table)
{
var columns = parser.Expect<Scalar>();
if (columns.Value != "rows")
{
throw new YamlException(columns.Start, columns.End,
"Expected a scalar named 'rows'");
}
parser.Expect<SequenceStart>();
while (parser.Allow<SequenceEnd>() == null)
{
var row = table.NewRow();
var columnIndex = 0;
parser.Expect<SequenceStart>();
while (parser.Allow<SequenceEnd>() == null)
{
var value = parser.Expect<Scalar>();
var columnType = table.Columns[columnIndex].DataType;
row[columnIndex] = TypeConverter.ChangeType(value.Value, columnType);
++columnIndex;
}
table.Rows.Add(row);
}
}
public void WriteYaml(IEmitter emitter, object value, Type type)
{
var table = (DataTable)value;
emitter.Emit(new MappingStart());
EmitColumns(emitter, table);
EmitRows(emitter, table);
emitter.Emit(new MappingEnd());
}
private static void EmitColumns(IEmitter emitter, DataTable table)
{
emitter.Emit(new Scalar("columns"));
emitter.Emit(new MappingStart(null, null, true, MappingStyle.Block));
foreach (DataColumn column in table.Columns)
{
emitter.Emit(new Scalar(column.ColumnName));
emitter.Emit(new Scalar(column.DataType.AssemblyQualifiedName));
}
emitter.Emit(new MappingEnd());
}
private static void EmitRows(IEmitter emitter, DataTable table)
{
emitter.Emit(new Scalar("rows"));
emitter.Emit(new SequenceStart(null, null, true, SequenceStyle.Block));
foreach (DataRow row in table.Rows)
{
emitter.Emit(new SequenceStart(null, null, true, SequenceStyle.Flow));
foreach (var item in row.ItemArray)
{
var value = TypeConverter.ChangeType<string>(item);
emitter.Emit(new Scalar(value));
}
emitter.Emit(new SequenceEnd());
}
emitter.Emit(new SequenceEnd());
}
}
它使用如下:
var table = new DataTable();
table.Columns.Add("id", typeof(int));
table.Columns.Add("name", typeof(string));
table.Columns.Add("description", typeof(string));
table.Rows.Add(1, "first", "The first row");
table.Rows.Add(2, "second", "The second row");
// Serialize
var serializer = new SerializerBuilder()
.WithTypeConverter(new DataTableTypeConverter())
.Build();
var yaml = serializer.Serialize(table);
// Deserialize
var deserializer = new DeserializerBuilder()
.WithTypeConverter(new DataTableTypeConverter())
.Build();
var parsedTable = deserializer.Deserialize<DataTable>(yaml);
此示例中的序列化YAML是:
columns:
id: System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
name: System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
description: System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089
rows:
- [1, first, The first row]
- [2, second, The second row]
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