DataSet does not support System.Nullable<> in Export

Thanks to a C# version of a generating a datatable and some hacking around, I can offer this answer in VB - I put it on here because I've just had a lot of hassle wanting to get a filterable dataset from a stored proc whilst using a simple datalayer. I hope it helps someone else!

Note: The use case is where you wish to use BindingSource.Filter = "some query string":

Imports System.Reflection

Public Module Extenders
<System.Runtime.CompilerServices.Extension>
Public Function ToDataTable(Of T)(collection As IEnumerable(Of T), tableName As String) As DataTable
    Dim tbl As DataTable = ToDataTable(collection)
    tbl.TableName = tableName
    Return tbl
End Function

<System.Runtime.CompilerServices.Extension>
Public Function ToDataTable(Of T)(collection As IEnumerable(Of T)) As DataTable
    Dim dt As New DataTable()

    Dim tt As Type = GetType(T)
    Dim pia As PropertyInfo() = tt.GetProperties()

    'Create the columns in the DataTable

    For Each pi As PropertyInfo In pia
        Dim a = 
If(Nullable.GetUnderlyingType(pi.PropertyType), pi.PropertyType)
        dt.Columns.Add(pi.Name, If(Nullable.GetUnderlyingType(pi.PropertyType), pi.PropertyType))
    Next

    'Populate the table

    For Each item As T In collection
        Dim dr As DataRow = dt.NewRow()
        dr.BeginEdit()

        For Each pi As PropertyInfo In pia

            dr(pi.Name) = If(Nullable.GetUnderlyingType(pi.PropertyType) Is GetType(DateTime), DBNull.Value, pi.GetValue(item, Nothing))
        Next
        dr.EndEdit()
        dt.Rows.Add(dr)
    Next
    Return dt
End Function

End Module

try with

dt.Columns.Add(pi.Name, Nullable.GetUnderlyingType(
            pi.PropertyType) ?? pi.PropertyType);

I would search for nullable and replace it with a string which can be null unlike a DateTime.

foreach (PropertyInfo pi in properties)
{
    if (pi.PropertyType.Name.Contains("Nullable"))
       myDataType = typeof(String);
    else
       myDataType = pi.PropertyType;
}

Here is a complete version:

private DataTable CreateDataTable(PropertyInfo[] properties)
{
    DataTable dt = new DataTable();
    DataColumn dc = null;
    foreach (PropertyInfo pi in properties)
    {
        dc = new DataColumn();
        dc.ColumnName = pi.Name;

        if (pi.PropertyType.Name.Contains("Nullable"))
            dc.DataType = typeof(String);
        else
            dc.DataType = pi.PropertyType;

        // dc.DataType = pi.PropertyType;
        dt.Columns.Add(dc);
    }
    return dt;
}