Question

I’m relatively new to C# – but come from a C/C++ background.

I need a data type (class) that is similar to DataTable, but allows the stored columns to hold “simple” types (int, float, boolean, [string]) AS WELL as data of the same type (so that a column could hold another table which also has columns that stores tables etc).

In C++ parlance, what I am describing is something along these lines:

typedef union { /*... */ } ValueType;
typedef std::vector<ValueType> ColumnValues; 

class Column
{
    private:
       std::string m_name ;
       ColumnValues m_values;

    public:
       Column(const std::string& name);
       // ...
}

class Table
{
   private:
      std::string m_name;
      std::vector<Column> m_cols;

    public:
       Table(const std::string& name, const std::vector<Column> *cols_ptr = NULL);
       // ...   
};

A column can hold any valid data type – which includes a Table data type (hence the implicit infinite nesting capability).

My initial thought approach was to inherit from DataTable – but thought I’d com in here to check if:

1. If such a class already exists somewhere (either in the .Net library or elsewhere)
2. if that is the correct way of going about it

In the event that I will need to “roll my own”, I would appreciate some pointers (i.e. code snippets) to help me get started.

[Edit]

Proposed usage: I intend to use this data type primarily to serialize objects in my library (so I can send them in message packets etc), but also, so I can use them as a kind of data dictionary that allows me to store data of arbitrary complexity.

Answer 1

I am not sure if I’m understanding corrrectly, but what is preventing you from creating a DataColumn with DataTable as it’s type?

Something like the following:

DataTable myTableOfTables = new DataTable("TableOfTables);
myTableOfTables.Columns.Add(new DataColumn("Table", typeof(DataTable)));

Now you can go ahead and do the following:

myTableOfTables.Rows.Add(myTableOfTables.NewRow()[0] = new DataTable("NestedTable"));

And sure enough if you check in the immeadiate window:

? myTableOfTables.Rows[0][0]

You will get:

{NestedTable}
    base {System.ComponentModel.MarshalByValueComponent}: {NestedTable}
    CaseSensitive: false
    ChildRelations: {System.Data.DataRelationCollection.DataTableRelationCollection}
    Columns: {System.Data.DataColumnCollection}
    Constraints: {System.Data.ConstraintCollection}
    DataSet: null
    DefaultView: {System.Data.DataView}
    DisplayExpression: ""
    ExtendedProperties: Count = 0
    HasErrors: false
    IsInitialized: true
    Locale: {es-ES}
    MinimumCapacity: 50
    Namespace: ""
    ParentRelations: {System.Data.DataRelationCollection.DataTableRelationCollection}
    Prefix: ""
    PrimaryKey: {System.Data.DataColumn[0]}
    RemotingFormat: Xml
    Rows: {System.Data.DataRowCollection}
    Site: null
    TableName: "NestedTable"

So you already have a class that allows this kind of structure: DataTable

If what you want is one DataColumn that is able to contain whatever value, be it an int, a string or what have you, then simply define its type as object.