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如何在vb.net中使用数据读取器

vb.net database mysql

user225269 · 技术社区 · 15 年前

请帮助,如何在vb.net中真正使用数据读取器。我正在使用odbc连接mysql和vb.net。

Public Function form2search(ByVal drugname As String) As OdbcDataReader

        cmd.CommandText = "SELECT *  FROM drug WHERE Drug_name LIKE'%" & drugname & "' "
        Return cmd.ExecuteReader

    End Function

文本更改事件:

con.drugname=textBoxdrugname.text
     Dim rdr As Odbc.OdbcDataReader
            rdr = con.form2search(drugname)
        if rdr.hasrows=true then
        rdr.read()

        TextBoxdrugname.Text = rdr("Drug_name").ToString
                        TextBoxdrugcode.Text = rdr("Drug_code").ToString
                        drugtype.Text = rdr("Drug_type").ToString

        end if

2 回复 | 直到 15 年前

Jürgen Steinblock 15 年前

DataReader是一个低级实现,不支持导航,每次调用时只读取一行

reader.Read()

对于Windows窗体应用程序,您可能应该使用数据集/数据表方法或ORM。您应该考虑在odbc驱动程序上使用mysql连接器网络。可以在mysql.com上找到。

dim table as new DataTable("table1")

' Create a Connection
using conn as new MysqlConnection("...connectionstring")
    conn.Open() ' Open it

    ' Create a new Command Object
    using cmd as new MysqlCommand("SELECT * FROM table", conn)

        ' Create a DataAdapter
        ' A DataAdapter can fill a DataSet or DataTable
        ' and if you use it with a CommandBuilder it also
        ' can persist the changes back to the DB with da.Update(...)
        using da as new MysqlDataAdapter(cmd)
            da.Fill(table) ' Fill the table
        end using

    end using
end using

' A Binding Source allows record navigation
dim bs as new BindingSource(table, nothing)

' You can bind virtually every property (most common are "text" "checked" or "visible"
' of a windows.forms control to a DataSource
' like a DataTable or even plain objects
textBox1.DataBindings.Add("Text", bs, "columnName")

' Now you can navigate your data
bs.MoveNext()

' Even a ComboBox can be bound to a List and display the related value
' of your current row
comboBox1.DataSource = table2
comboBox1.DisplayMember = "name"
comboBox1.ValueMember = "id"

comboBox1.DataBindings.Add("SelectedValue", bs, "id")

Rupeshit 15 年前

您只需将数据读取器的对象放入while循环。以下是示例代码:

      dr = myCommand.ExecuteReader()
      While dr.Read()
      'reading from the datareader
       MessageBox.Show("colname1" & dr(0).ToString())
       MessageBox.Show("colname2" & dr(1).ToString())
       MessageBox.Show("colname3" & dr(2).ToString())
       MessageBox.Show("colname4" & dr(3).ToString())
       MessageBox.Show("colname5" & dr(4).ToString())
      'displaying the data from the table
       End While
       dr.Close()