.NET - Convert Generic Collection to DataTable

Question

I am trying to convert a generic collection (List) to a DataTable. I found the following code to help me do this:

// Sorry about indentation
public class CollectionHelper
{
private CollectionHelper()
{
}

// this is the method I have been using
public static DataTable ConvertTo<T>(IList<T> list)
{
    DataTable table = CreateTable<T>();
    Type entityType = typeof(T);
    PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);

    foreach (T item in list)
    {
        DataRow row = table.NewRow();

        foreach (PropertyDescriptor prop in properties)
        {
            row[prop.Name] = prop.GetValue(item);
        }

        table.Rows.Add(row);
    }

    return table;
}    

public static DataTable CreateTable<T>()
{
    Type entityType = typeof(T);
    DataTable table = new DataTable(entityType.Name);
    PropertyDescriptorCollection properties = TypeDescriptor.GetProperties(entityType);

    foreach (PropertyDescriptor prop in properties)
    {
        // HERE IS WHERE THE ERROR IS THROWN FOR NULLABLE TYPES
        table.Columns.Add(prop.Name, prop.PropertyType);
    }

    return table;
}
}

My problem is that when I change one of the properties of MySimpleClass to a nullable type, I get the following error:

DataSet does not support System.Nullable<>.

How can I do this with Nullable properties/fields in my class?

Answer 1

Then presumably you'll need to lift them to the non-nullable form, using Nullable.GetUnderlyingType, and perhaps change a few null values to DbNull.Value...

Change the assignment to be:

row[prop.Name] = prop.GetValue(item) ?? DBNull.Value;

and when adding the columns to be:

table.Columns.Add(prop.Name, Nullable.GetUnderlyingType(
            prop.PropertyType) ?? prop.PropertyType);

And it works. (?? is the null-coalescing operator; it uses the first operand if it is non-null, else the second operand is evaluated and used)