sql - vb.net 从数据库中读取数据

Question

所以我使用这段示例代码从 MS Access 数据库中检索数据并将其显示在表单的几个文本框中。出现以下错误 -

@ dr = cmd.ExecuteReader - Data type mismatch in criteria expression. dr = cmd.ExecuteReader

这是示例代码 -

Dim provider As String
Dim dataFile As String
Dim connString As String
Public myConnection As OleDbConnection = New OleDbConnection
Public dr As OleDbDataReader

Private Sub Form1_Load(sender As Object, e As EventArgs) Handles MyBase.Load
    provider = "Provider=Microsoft.ACE.OLEDB.12.0;Data Source ="
    dataFile = "C:\Users\example\Desktop\Data.accdb" ' Change it to your Access Database location
    connString = provider & dataFile
    myConnection.ConnectionString = connString
End Sub

Dim r As Random = New Random

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    myConnection.Open()
    TextBox1.Clear()
    TextBox2.Clear()
    TextBox3.Clear()
    Dim str As String
    str = "SELECT * FROM Items WHERE (Code = '" & r.Next(1, 3) & "')"
    Dim cmd As OleDbCommand = New OleDbCommand(str, myConnection)
    dr = cmd.ExecuteReader
    While dr.Read()
        TextBox1.Text = dr("Description").ToString
        TextBox2.Text = dr("Cost").ToString
        TextBox3.Text = dr("Price").ToString
    End While
    myConnection.Close()
End Sub

Answer 1

试试这个..

str = "SELECT * FROM Items WHERE (Code = '"& (r.Next(1, 3)).ToString() & "')"