getting data from mysql database by using thread in vb.,net - vb.net

Question

I'm trying to get data from database but I got an error:
There is already an open DataReader associated with this Connection
which must be closed first
what I did is the following codes:
1: I have a module that contains the following sub:
Public Function CheckServerConn() As Boolean
Try
_ServerConnStr = New MySqlConnection(My.Settings.DbPath)
If _ServerConnStr.State = ConnectionState.Open Then
_ServerConnStr.Close()
End If
If _ServerConnStr.State = ConnectionState.Closed Then
_ServerConnStr.Open()
Return True
End If
Catch ex As Exception
MsgBox("Check The Conn " & ex.Message, Me_MsgInfoStyle, Me_MsgCaptionStr)
Return False
End Try
#Disable Warning BC42353 ' Function doesn't return a value on all code paths
End Function
2: I have this subroutine in class called "ClsMySql":
'GetData
Public Sub GetData(ByVal SqlStr As String, ByVal xDt As DataTable, ByVal xPar() As MySqlParameter)
Using xCmd As New MySqlCommand() With {
.CommandType = CommandType.Text,
.CommandText = SqlStr,
.Connection = _ServerConnStr,
.CommandTimeout = 5000000
}
If xPar IsNot Nothing Then
For i As Integer = 0 To xPar.Length - 1
xCmd.Parameters.Add(xPar(i))
Next
End If
Using xDa As New MySqlDataAdapter(xCmd)
xDa.Fill(xDt)
End Using
xDt.Dispose()
End Using
End Sub
3: I have a class for the table that have the following method:
Public Sub MySql_Get_Daf()
xClsMySql = New ClsMySql
Dim SqlStr As String = "SELECT RegID,RegType, tblregs1.`RegRef`,`RegDate`, COUNT(`RegdID`) AS xCount
,IF(COUNT(`RegdID`) =3,'Ok','Error') AS xResult FROM tblregs1
INNER JOIN tblregs2 ON tblregs2.RegRef = tblregs1.RegRef
WHERE `RegType` = 'Daf'
GROUP BY tblregs1.`RegRef`
ORDER BY COUNT(`RegdID`) ASC"
Dt_Get_Daf = New DataTable()
xClsMySql.GetData(SqlStr, Dt_Get_Daf, Nothing)
End Sub
Public Sub MySql_Get_Qbd()
xClsMySql = New ClsMySql
Dim SqlStr As String = "SELECT RegID,RegType, tblregs1.`RegRef`,`RegDate`, COUNT(`RegdID`) AS xCount
,IF(COUNT(`RegdID`) =3,'Ok','Error') AS xResult FROM tblregs1
INNER JOIN tblregs2 ON tblregs2.RegRef = tblregs1.RegRef
WHERE `RegType` = 'Qbd'
GROUP BY tblregs1.`RegRef`
ORDER BY COUNT(`RegdID`) ASC"
Dt_Get_Qbd = New DataTable()
xClsMySql.GetData(SqlStr, Dt_Get_Qbd, Nothing)
End Sub
Public Sub MySql_Get_All()
Dim xThread As Thread = New Thread(Sub() MySql_Get_Daf())
Dim xThread2 As Thread = New Thread(Sub() MySql_Get_Qbd())
xThread.Start()
xThread2.Start()
End Sub
when I call MySql_Get_All by a button it gives me the next error:
There is already an open DataReader associated with this Connection
which must be closed first
can anybody tell me what's the wrong here