sqlCommand.ExecuteNonQuery返回sql语句影响行数问题

sqlCommand.ExecuteNonQuery返回sql语句影响行数问题
Public Shared Function sqlcon_Executeint(ByVal sql As String) As Integer '执行sql更新语句并返回影响行数,当为select语句时，请用count(*)样式
Using sqlcmd As New SqlCommand
Dim sqlCommand As System.Data.SqlClient.SqlCommand = New System.Data.SqlClient.SqlCommand(sql, sqlcon)
Dim rowsAffected As Integer = 0
sqlcon.Open()
Try
If sqlCommand.ExecuteNonQuery <> -1 Then '判断是否是查询语句
rowsAffected = sqlCommand.ExecuteNonQuery '
Else '是查询语句
rowsAffected = sqlCommand.ExecuteScalar
End If
Catch ex As Exception
WriteErr(ex, sql)
Throw New NotSupportedException(ex.ToString)
Finally
sqlcon.Close()
End Try
Return rowsAffected
End Using
End Function
问题：修改，插入语句的返回值正确，删除语句的返回值始终为“0”注：sql返回的为-1（ado.net）