How can get correct Column Name from Database with Npgsql?

Question

This is my table in database:

CREATE TABLE public.test
(
  id integer NOT NULL DEFAULT nextval('test_id_seq'::regclass),
  hc character varying(30),
  "Hc" character varying(30),
  "HC" character varying(30),
  f character varying(30),
  "F" character varying(30),
  f1 character varying(30),
  te numeric(2,2),
  CONSTRAINT test_pkey PRIMARY KEY (id)
)

If i get a Table Definition by Npgsql from vb.net:

select * from test where null = null

Result: some colums had changed name: Ex: Hc => Hc1,HC => HC2

How can get correct Column Name from Database with Npgsql?

Answer 1

您似乎（直接或间接）使用DbDataAdapter.Fill，如果需要，它会按以下方式重命名列：

  

如果DbDataAdapter在填充a时遇到重复的列   DataTable，它使用   模式“ columnname1”，“ columnname2”，“ columnname3”，等等。

很明显，此重复数据删除过程以不区分大小写的方式处理列名，这就是在示例中也对列进行重命名的原因。无法直接关闭此行为（请参见AdapterUtil.cs,2402）。

一种解决方法是使用附加的SqlCommand并使用SqlDataReader.GetName获得确切的列名，然后相应地更改DataTable的列。可以按照以下步骤进行：

Dim query = "select * from test where null = null"

' setup connection
Dim connection As New NpgsqlConnection(
    String.Format("Server={0};Port={1};Database={2};User Id={3};Password={4};",
                  host, port, database, user, password))
connection.Open()

' fill data table from query
Dim table As New DataTable
Using adapter = New NpgsqlDataAdapter(query, connection)
    adapter.Fill(table)
End Using

' correct column names
Using command = New NpgsqlCommand(query, connection)
    Using reader = command.ExecuteReader()
        For i = 0 To table.Columns.Count - 1
            table.Columns(i).ColumnName = reader.GetName(i)
        Next
    End Using
End Using

' display table in DataGridView
view.DataSource = table