如何自动生成vb.net中的id列 [英] how to autogenerate id column in vb.net

问题描述

我想在我的项目数据库中自动生成一个id列，我正在使用以下代码，但是它不起作用.
我在数据库中将"Id"列设置为"Int".
它给了我一个例外，因为从字符串到双精度的转换无效"

I want to auto generate an id column in my project database I am using the following code, but it is not working.
I have Set "Id" column as "Int" in my Database.
It is giving me an exception as "Conversion From String To Double is Not Valid"

Private Sub BtnAdd_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        conn.Open()
        Dim query As String = "insert into Academic(Id,Session)values(@Id,@Session)"
        If TxtSession.Text = "" Then
            MsgBox("Please Insert the Session ", MsgBoxStyle.Information, "Grading System")
            TxtSession.Text = ""
            txtSessionId.Text = ""
            TxtSession.Focus()
        Else

            Dim query1 As String = "select Id,Session from Academic Where Session='" & TxtSession.Text & "'"
            cmd1 = New SqlCommand(query1, conn)
            dr = cmd1.ExecuteReader()
            If dr.Read = False Then
                dr.Close()
                Try
                    
                    Try
                        Dim no As integer
                        Dim k as integer
                        cmd = New SqlCommand("select count(*) from Academic", conn)
                        no = cmd.ExecuteScalar
                        
                        no = CInt(no) + 1

                       
                        If no > 0 And no <= 9 Then
                            k = ("A000" + no)
                        ElseIf no > 9 And no <= 99 Then
                            k = ("A00" + no)
                        ElseIf no > 99 And no <= 999 Then
                            k = ("A0" + no)
                        Else
                            k = ("A" + no)
                        End If
                    Catch ex As Exception
                        MsgBox(ex.Message)

                    End Try

                    cmd = New SqlCommand(query, conn)
                    dr.Close()
                    cmd.Parameters.AddWithValue("@Id", (k))
                    cmd.Parameters.AddWithValue("@Session", (TxtSession.Text))
                    cmd.ExecuteNonQuery()
                    MsgBox("Session Inserted", MsgBoxStyle.Information, "Grading System")
                    ds.Clear()
                    conn.Close()
                    LoadDataInDataGrid()
                    TxtSession.Text = ""
                    TxtSession.Focus()

                Catch ex As Exception
                    MessageBox.Show(ex.ToString())
                Finally
                    If conn.State = ConnectionState.Open Then
                        conn.Close()
                    End If
                End Try
            Else
                MsgBox("Record Exists", MsgBoxStyle.Information, "Grading System")
                TxtSession.Focus()
                txtSessionId.Text = ""

            End If
        End If
        conn.Close()
    End Sub

推荐答案

是因为异常告诉您.
您正在尝试将字符串(k)存储到int字段(Id)中.
将字段更改为字符串或更改代码以生成类型为int的ID.

Is it as the exception is telling you.
You are trying to store a string (k) into a int field (Id).
Either change the field to a string or change the code to generate id of type int.

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