Fill a Datatable from a list of a complex type

Question

I’m looking to create a method that gets a list of some kind of complex List<T> and return a datatable with all the data. In my code I managed to get here.

protected virtual DataTable buildDataTableFromComplexTypeList<T> ( string tableName, List<T> complexList )
{
    DataTable dataTable = new DataTable ( tableName );
    PropertyInfo[] properties = typeof ( T ).GetProperties ( ); // Getting the metadata through reflection (System.Reflection)

    foreach ( PropertyInfo property in properties ) // Create DataTableColumns from the T properties
        dataTable.Columns.Add ( property.Name, property.PropertyType );

    DataRow dataRow;

    foreach ( T item in complexList )
    {
        dataRow = dataTable.NewRow ( ); // Create new DataRow with the same columns of DataTable
        dataRow[]
    }
}

Notice that on the first foreach I used Reflection to create the columns, but now I don’t know how to fill in the data.

Answer 1

Besides catching the PropertyType you have to check if he is Nullable, so I slightly modified your first is to make this check and add when needed.

To create the rows just create an array in the same sequences that created the columns of the DataTable and then add this array with the following command dataTable.Rows.Add(array)

protected virtual DataTable buildDataTableFromComplexTypeList<T>(string tableName, List<T> complexList)
{
    DataTable dataTable = new DataTable(tableName);
    PropertyInfo[] properties = typeof(T).GetProperties(); 

    foreach (PropertyInfo property in properties)
    {
        var type = (property.PropertyType.IsGenericType && property.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>) ? Nullable.GetUnderlyingType(property.PropertyType) : property.PropertyType);
        dataTable.Columns.Add(property.Name, type );

    }

    foreach (T item in complexList)
    {
        var values = new object[properties.Length];
        for (int i = 0; i < properties.Length; i++)
        {
            values[i] = properties[i].GetValue(item, null);
        }
        dataTable.Rows.Add(values);
    }

    return dataTable;
}

Answer 2

The same way you used Reflection to recover generic type properties, you can also use Reflection to recover the value of the property for an instance of that type, it would look like this:

protected virtual DataTable buildDataTableFromComplexTypeList<T>(string tableName, List<T> complexList)
{
    DataTable dataTable = new DataTable(tableName);
    PropertyInfo[] properties = typeof(T).GetProperties(); // Getting the metadata through reflection (System.Reflection)

    foreach (PropertyInfo property in properties) // Create DataTableColumns from the T properties
    {
        var type = (property.PropertyType.IsGenericType && property.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>) ? Nullable.GetUnderlyingType(property.PropertyType) : property.PropertyType);
        dataTable.Columns.Add(property.Name, type);
    }

    DataRow dataRow;

    foreach (T item in complexList)
    {
        dataRow = dataTable.NewRow(); // Create new DataRow with the same columns of DataTable
                                        // novas linhas
        foreach (PropertyInfo property in properties)
            dataRow[property.Name] = property.GetValue(item) ?? DBNull.Value;

        dataTable.Rows.Add(dataRow);
    }

    // nova linha
    return dataTable;
}

If you want, you can do the same using Linq

protected virtual DataTable buildDataTableFromComplexTypeList<T>(string tableName, List<T> complexList)
{
    DataTable tabela = new DataTable();
    PropertyInfo[] propriedades = typeof(T).GetProperties();

    tabela.Columns.AddRange(
        propriedades.Select(p => new DataColumn(p.Name, (p.PropertyType.IsGenericType && p.PropertyType.GetGenericTypeDefinition() == typeof(Nullable<>) ? Nullable.GetUnderlyingType(p.PropertyType) : p.PropertyType))).ToArray()
        );

    complexList.ForEach(
        i => tabela.Rows.Add(
            propriedades.Select(p => p.GetValue(i) ?? DBNull.Value).ToArray()
            )
        );

    return tabela;
}

I adjusted the answer with the placement of @Jeferson Almeida on Nullable because I remember I’ve had problems with that in the past.

Sources:
Get Property value from string using Reflection in C#
LINQ: IENUMERABLE TO DATATABLE