Vb.net 参数化查询“（@username nvarchar（4000））UPDATE Seller Set Status='deactivated'需要未提供的参数“@username”

嗨，我的代码有问题，我无法解决问题。如果有人能帮忙的话。谢谢

Protected Sub btnActive_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnActive.Click

Dim connectionString As String = "Data Source = .\SQLEXPRESS; AttachDbFileName=|DataDirectory|Petite.mdf; Integrated Security=True; User Instance=True"

Dim conn As SqlConnection = New SqlConnection(connectionString)

Dim cmd As SqlCommand

Dim myupdate As String

    myupdate = " UPDATE Seller Set Status='active' WHERE Username=@Username"

        cmd = New SqlCommand(myupdate, conn)
    cmd.Parameters.AddWithValue("@Username", Session("Username"))

        conn.Open()
        cmd.ExecuteNonQuery()

    MsgBox("Account has been successfully activated!!")

    Response.Redirect("AdminSellers.aspx")
        conn.Close()
End Sub

我得到了这个错误

参数化查询'@username NVARCH4000 UPDATE Seller Set Status='deactivated'需要未提供的参数'@username'

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SessionUsername是否可能为Nothing？我怀疑这会触发此行为根据消息，错误是在调用“deactivated”查询时。您正在向我们显示“活动”查询。也许代码不一样……哇，敏锐的眼睛@LarsTech！传递给AddWithValue的会话变量？嗯，真臭，你在地雷上，希望一切顺利。我建议创建一个参数，精确指定类型和大小，并将会话变量转换为适当的C类型