mysql - 将从 mysql 查询获得的值显示到 VB.net 文本框中

Question

我试图在 vb.net 的文本框中显示我从 COUNT(*) 查询中获得的值，但不是显示获得的值，而是显示实际查询。

这是我的代码:

Imports MySql.Data.MySqlClient
Public Class Statistics
Dim conn As MySqlConnection
Dim command As MySqlCommand
Dim query As String
Dim dadapter As New MySqlDataAdapter

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    conn = New MySqlConnection
    conn.ConnectionString =
        "server=localhost;userid=root;database=librarydatabase"
    Dim reader As MySqlDataReader


    Try
        conn.Open()
        query = "SELECT COUNT(*) FROM login where users='" & Username.Text & "'"


        command = New MySqlCommand(query, conn)
        reader = command.ExecuteReader

        dadapter.SelectCommand = command
        If reader.HasRows Then
            reader.Read()
            takenout.Text = (query)


        End If

        conn.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Dispose()

    End Try

End Sub

这是我的程序的屏幕截图:

当尝试修复代码时，我将其更改为将 takenout.Text = (query) 替换为 takenout.Text = (reader.read()) 并删除上面的 reader.read()) 和 dadapter.SelectCommand = command

这里是修改后的代码:

Imports MySql.Data.MySqlClient

Public Class Statistics
Dim conn As MySqlConnection
Dim command As MySqlCommand
Dim query As String
Dim dadapter As New MySqlDataAdapter

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    conn = New MySqlConnection
    conn.ConnectionString =
        "server=localhost;userid=root;database=librarydatabase"
    Dim reader As MySqlDataReader

    Try
        conn.Open()
        query = "SELECT COUNT(*) FROM login where users='" & Username.Text & "'"


        command = New MySqlCommand(query, conn)
        reader = command.ExecuteReader


        If reader.HasRows() Then

            takenout.Text = (reader.Read())


        End If

        conn.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)
    Finally
        conn.Dispose()

    End Try

End Sub

此代码没有解决问题，而是在按下按钮时无论用户名文本框中的内容如何，​​都会在文本框中显示 true。

这是一张图片:

Answer 1

改用 command.ExecuteScalar()。