我的项目中的 VB.NET + MYSQL + CRUD 出错

Posted 2023-02-25

【中文标题】我的项目中的 VB.NET + MYSQL + CRUD 出错

【英文标题】：Error in VB.NET + MYSQL + CRUD in my project

【发布时间】：2021-04-28 20:07:44

【问题描述】：

您好，我正在处理一个 crud 项目，但出现错误显示一条消息：Vbmysql_SMART_CRUD.exe 中发生了“System.TypeInitializationException”类型的未处理异常

和指向此的黄色区域： sql = "SELECT auto_id, first_name, last_name, CONCAT(first_name, ' ', last_name) AS 'full_name', gender FROM tbl_smart_crud" & "WHERE CONCAT(first_name, ' ', last_name) LIKE @keyword1 OR gender = @keyword2 ORDER BY auto_id ASC"

这是完整的代码，请告诉我这里出了什么问题：

Option Explicit On
Option Strict On

Imports MySql.Data.MySqlClient

Public Class Form1

    Private ID As String = ""
    Private intRow As Integer = 0

    Private Sub Form1_Load(sender As Object, e As 
EventArgs) Handles MyBase.Load
        ResetMe()
        LoadData()
    End Sub

    Private Sub ResetMe()

        Me.ID = ""
        FirstNameTextBox.Text = ""
        LastNameTextBox.Text = ""


        If GenderComboBox.Items.Count > 0 Then
            GenderComboBox.SelectedIndex = 0
        End If

        UpdateButton.Text = "Update()"
        DeleteButton.Text = "Delete()"

        KeywordTextBox.Clear()
        KeywordTextBox.Select()

    End Sub

Private Sub Execute(Mysql As String, Optional Parameter As String = "")
    cmd = New MySqlCommand(Mysql, con)
    Addparameters(Parameter)
    performcrud(cmd)
End Sub


Private Sub Addparameters(str As String)
    cmd.Parameters.Clear()
    cmd.Parameters.AddWithValue("FirstName", FirstNameTextBox.Text.Trim())
    cmd.Parameters.AddWithValue("LastName", LastNameTextBox.Text.Trim())
    cmd.Parameters.AddWithValue("Gender", GenderComboBox.SelectedItem.ToString())

    If str = "Update" Or str = "Delete" And Not String.IsNullOrEmpty(Me.ID) Then
        cmd.Parameters.AddWithValue("ID", Me.ID)
    End If

End Sub

Private Sub InsertButton_Click(sender As Object, e As EventArgs) Handles InsertButton.Click

    If String.IsNullOrEmpty(FirstNameTextBox.Text.Trim()) Or String.IsNullOrEmpty(LastNameTextBox.Text.Trim()) Then
        MsgBox("Por Favor Escreva As Informaçoes Em Falta. ", MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation,
               "Nova Estrela - Dados Do Produto")
        Exit Sub
    End If

    sql = "INSERT INTO tbl_smart_crud(first_name, last_name, gender) VALUES(@FirstName, @LastName, @Gender)"

    Execute(sql, "Insert")

    MsgBox("Muito Obrigado... O registro Acima Foi Salvo Com Exito! ", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
            "Nova Estrela - Dados Do Produto")

    LoadData()

    ResetMe()

End Sub

Private Sub LoadData(Optional keyword As String = "")


    sql = "SELECT auto_id, first_name, last_name, CONCAT(first_name, ' ', last_name) AS 'full_name', gender FROM tbl_smart_crud" &
     "WHERE CONCAT(first_name, ' ', last_name) LIKE @keyword1 OR gender = @keyword2 ORDER BY auto_id ASC"

    Dim strKeyword As String = String.Format("%0%", keyword)

    cmd = New MySqlCommand(sql, con)
    cmd.Parameters.Clear()
    cmd.Parameters.AddWithValue("keyword1", strKeyword)
    cmd.Parameters.AddWithValue("keyword2", keyword)

    Dim dt As DataTable = performcrud(cmd)

    If dt.Rows.Count > 0 Then
        intRow = Convert.ToInt32(dt.Rows.Count.ToString())
    Else
        intRow = 0
    End If

    ToolStripStatusLabel1.Text = "Numero De Registro(s): " & intRow.ToString()

    With DataGridView1

        .MultiSelect = False
        .SelectionMode = DataGridViewSelectionMode.FullRowSelect
        .AutoGenerateColumns = True


        .DataSource = dt

        .Columns(0).HeaderText = "ID"
        .Columns(0).HeaderText = "FirstName"
        .Columns(0).HeaderText = "LastName"
        .Columns(0).HeaderText = "FullName"
        .Columns(0).HeaderText = "Preco De Compra"
        .Columns(0).HeaderText = "Gender"

        .Columns(0).Width = 85
        .Columns(0).Width = 170
        .Columns(0).Width = 170
        .Columns(0).Width = 220
        .Columns(0).Width = 100

    End With

End Sub

Private Sub DataGridView1_CellClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.DataGridViewCellEventArgs) Handles DataGridView1.CellClick

    Try

        Dim dgv As DataGridView = DataGridView1

        If e.RowIndex <> -1 Then

            Me.ID = Convert.ToString(dgv.CurrentRow.Cells(0).Value).Trim()
            UpdateButton.Text = "Update(" & Me.ID & ")"
            DeleteButton.Text = "Delete(" & Me.ID & ")"

            FirstNameTextBox.Text = Convert.ToString(dgv.CurrentRow.Cells(1).Value).Trim()
            LastNameTextBox.Text = Convert.ToString(dgv.CurrentRow.Cells(2).Value).Trim()

            GenderComboBox.SelectedItem = Convert.ToString(dgv.CurrentRow.Cells(4).Value).Trim()

        End If

    Catch ex As Exception

    End Try

End Sub


Private Sub UpdateButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles UpdateButton.Click

    If DataGridView1.Rows.Count = 0 Then
        Exit Sub
    End If

    If String.IsNullOrEmpty(Me.ID) Then
        MsgBox("Por Favor Escolha Um Produto ou Artigo Na Lista.", MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation,
                "Nova Estrela - Actualizando Dados Do Produto")
        Exit Sub
    End If

    If String.IsNullOrEmpty(FirstNameTextBox.Text.Trim()) Or String.IsNullOrEmpty(LastNameTextBox.Text.Trim()) Then
        MsgBox("Por Favor Escreva As Informaçoes Em Falta. ", MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation,
               "Nova Estrela - Actualizando Dados Do Produto")
        Exit Sub
    End If

    sql = "Update tbl_smart_crud Set first_name = @FirstName, last_name = @LastName, gender = @Gender WHERE auto_id = @ID"

    Execute(sql, "Update")

    MsgBox("O registro Acima Foi Actualizado Com Exito!", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
            "Nova Estrela - Actualizando Dados Do Produto")

    LoadData()

    ResetMe()

End Sub

Private Sub DeleteButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles DeleteButton.Click

    If DataGridView1.Rows.Count = 0 Then
        Exit Sub
    End If

    If String.IsNullOrEmpty(Me.ID) Then
        MsgBox("Por Favor Escolha Um Produto ou Artigo Na Lista.", MsgBoxStyle.OkOnly Or MsgBoxStyle.Exclamation,
                "Nova Estrela - Apagando Dados e Registro Do Produto")
        Exit Sub
    End If


    If MessageBox.Show("Queres Mesmo Deletar O Registro Seleccionado?", "Nova Estrela - Apagando Dados e Registro Do Produto",
                       MessageBoxButtons.YesNo, MessageBoxIcon.Question, MessageBoxDefaultButton.Button1) = DialogResult.Yes Then


        sql = "DELETE FROM add_product WHERE Codigo Do Produto = @Codigo Do Produto"

        Execute(sql, "Delete")

        MsgBox("O registro Foi Apagado Com Exito. ", MsgBoxStyle.OkOnly Or MsgBoxStyle.Information,
                "Nova Estrela - Apagando Dados e Registro Do Produto")

        LoadData()

        ResetMe()

    End If

End Sub

Private Sub SearchButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles SearchButton.Click


    If Not String.IsNullOrEmpty(KeywordTextBox.Text.Trim()) Then
        LoadData(KeywordTextBox.Text.Trim())
    Else
        LoadData()
    End If

    ResetMe()

End Sub

结束类

【问题讨论】：

我猜你给了我们整个程序的代码。您未能提供 performcrud 方法。无论如何，我们只需要发生错误的代码。尝试在其他表单级别变量所在的位置添加Private sql As String = ""。很抱歉，这段代码有很多问题。

【参考方案1】：

你没有声明变量sql

在Private intRow As Integer = 0之后写Private sql As String = ""

或者

在任何之前 sql = "something"写var sql = ""或var sql As String = ""

【讨论】：

我的朋友没用，它添加了 8 个错误（未声明 var，方法参数必须括在括号中）还有其他建议吗？