AutoComplete list is not showing same value but different in case for textbox control in VB.Net

See more:

C#

VB

.NET

auto-complete

I am using below code to show the list in AutoComplete.

Dim gridTextBox As TextBox = DirectCast(e.Control, TextBox)
gridTextBox.CharacterCasing = CharacterCasing.Normal
gridTextBox.AutoCompleteMode = AutoCompleteMode.SuggestAppend
gridTextBox.AutoCompleteSource = AutoCompleteSource.CustomSource
gridTextBox.AutoCompleteCustomSource = mAutocompleteLookupDescription.AutoCompleteSource

and the following line of code :

gridTextBox.AutoCompleteCustomSource = mAutocompleteLookupDescription.AutoCompleteSource

is giving me the correct number of list like

TEST1
test1
VALUE
value

but as soon as i am showing this in my gridview cell it's showing only once(removing the duplicate value), means it's removing the duplicate value which different in case.

Is it Autocomplete restriction from microsoft?, if yes, can i have the link which proves this.