How to fill a DataTable with a List(Of t) or convert a List(Of t) to a DataTable?

Question

I have read many posts on this topic; among them and most recently .NET - Convert Generic Collection to Data Table. Unfortunately, all to no avail.

I have a generic coll

Answer 1

The code you linked assumes the members are declared as properties. You didn't declare properties. You can make it work with Reflection:

Imports System.Reflection
...

      Public Shared Function ConvertToDataTable(Of T)(ByVal list As IList(Of T)) As DataTable
        Dim table As New DataTable()
        Dim fields() As FieldInfo = GetType(T).GetFields()
        For Each field As FieldInfo In fields
          table.Columns.Add(field.Name, field.FieldType)
        Next
        For Each item As T In list
          Dim row As DataRow = table.NewRow()
          For Each field As FieldInfo In fields
            row(field.Name) = field.GetValue(item)
          Next
          table.Rows.Add(row)
        Next
        Return table
      End Function

Answer 2

I have same issue than @SamSelikoff, moved to GetProperties:

Public Shared Function ConvertToDataTable(Of t)(
                                                  ByVal list As IList(Of t)
                                               ) As DataTable
    Dim table As New DataTable()
    If Not list.Any Then
        'don't know schema ....
        Return table
    End If
    Dim fields() = list.First.GetType.GetProperties
    For Each field In fields
        table.Columns.Add(field.Name, field.PropertyType)
    Next
    For Each item In list
        Dim row As DataRow = table.NewRow()
        For Each field In fields
            dim p = item.GetType.GetProperty(field.Name)
            row(field.Name) = p.GetValue(item, Nothing)
        Next
        table.Rows.Add(row)
    Next
    Return table
End Function

Answer 3

Following @Hans Passant function if anyone is dealing with nullable types:

For Each field As FieldInfo In fields
' Extra check for nullable
If field.FieldType.AssemblyQualifiedName.Contains("System.Nullable") Then
    ' Insert proper type
    If field.FieldType.AssemblyQualifiedName.Contains("System.DateTime") Then
       table.Columns.Add(field.Name, Type.GetType("System.DateTime"))
    End If
Else
    table.Columns.Add(field.Name, field.FieldType)
End If
Next

Values:

For Each item As T In list
Dim row As DataRow = table.NewRow()
For Each field As FieldInfo In fields
    ' Check if value is null
    If field.GetValue(item) is nothing Then
        Continue For
    End If
    row(field.Name) = field.GetValue(item)
Next
table.Rows.Add(row)
Next