在 VB.NET 中自动生成字母数字

Question

我目前正在处理我使用 VB.NET 2019 和 SQL Server 的项目。我需要创建一个自动生成 ID 的函数。

我希望我的 ID 如下所示：P001、P002、P003 等。有人可以告诉我如何编码吗？下面是我的代码

 Private Sub Form4_Load_1(sender As Object, e As EventArgs) Handles MyBase.Load
    BindData()
    Dim data As String = "Data Source=LAPTOP-M8KKSG0I;Initial Catalog=Oceania;Integrated Security=True"
    Dim con As New SqlConnection(data)
    Try
        If Con.State = ConnectionState.Closed Then
            con.Open()

        End If

        Dim sql As String = "Select Max(PatientID) from Patient"
        Dim cmd As New SqlCommand(sql, con)
        Dim Max As String = cmd.ExecuteScalar
        If Max > 0 Then
            TextBox1.Text = Max + 1
        Else
            TextBox1.Text = "P01"
        End If
    Catch ex As Exception
        MsgBox(Err.Description)
    End Try
End Sub

Answer 1

你可以这样试试。这里1 是一个自动生成的数字，它可能是 SQL Server 中表的标识键列值。

Dim number As Integer = 1
Dim numberText As String = "P" & number.ToString().PadLeft(3, "0") 

直播demo

您可以在表中添加这样的计算列来自动生成序列。一旦多人同时输入，这将减少重复值运行时的机会。

Alter table Patient ADD PatientCode AS ('P' + Convert(Varchar(3),CONCAT(REPLICATE('0', 3 - LEN(PatientID)), PatientID)) )

要动态获取列值，您可以尝试下面的代码来生成函数。

Private Sub GenerateSequnce()
    Dim constring As String = "Data Source=TestServer;Initial Catalog=TestDB;User id = TestUser;password=test@123"
    Using con As New SqlConnection(constring)
        Using cmd As New SqlCommand("Select Top 1 ISNULL(TaxCode, 0) from Tax_Mst Order By TaxCode Desc", con)
            cmd.CommandType = CommandType.Text
            Using sda As New SqlDataAdapter(cmd)
                Using dt As New DataTable()
                    sda.Fill(dt)
                    Dim maxNumberCode = dt.Rows(0)("TaxCode").ToString()
                    If (maxNumberCode = "0") Then
                        maxNumberCode = "1"
                    End If

                    Dim numberText As String = "P" & maxNumberCode.ToString().PadLeft(3, "0")
                End Using
            End Using
        End Using
    End Using
End Sub

这里TaxCode 的列是int 和identity 约束。

通过代码中的小修正，您可以实现如下所示。

Dim data As String = "Data Source=LAPTOP-M8KKSG0I;Initial Catalog=Oceania;Integrated Security=True"
        Dim con As New SqlConnection(data)
        Try
            If con.State = ConnectionState.Closed Then
                con.Open()
            End If

            Dim sql As String = "Select ISNULL(Max(PatientID), 0) from Patient"
            Dim cmd As New SqlCommand(sql, con)
            Dim Max As String = cmd.ExecuteScalar

            If (Max = "0") Then
                Max = "1"
            Else
                Max = CInt(Max) + 1
            End If
            Dim numberText As String = "P" & Max.ToString().PadLeft(3, "0")
            TextBox1.Text = numberText

        Catch ex As Exception
            MsgBox(Err.Description)
       End Try

输出