Question

我尝试调用一个方法来获取存储在会话中的数据库名称和数据。当我使用Server.MapPath("PayrollSystem_DB.mdb")检索数据库名称时，我得到一个nullreferenceexception。

我使用相同的代码在其他方法中传递数据库名称，它们工作正常。

// Sends data to SavePersonel() to write to personnel table
    if (clsDataLayer.SavePersonnel(Server.MapPath("PayrollSystem_DB.mdb"),
                                   Session["txtFirstName"].ToString(),
                                   Session["txtLastName"].ToString(),
                                   Session["txtPayRate"].ToString(),
                                   Session["txtStartDate"].ToString(),
                                   Session["txtEndDate"].ToString()))
    {
        txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                              "\nThe information was successfully saved!";

    }
    else
    {
        txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                             "\nThe information was NOT saved.";


    }

此代码获取frmPersonel中的数据，将其保存到会话并重定向到frmPersonelVerified

        //If nothing is added to the error message data is recorded to session.
        if (errorMessage == "")
        {
            //saves data to session
            Session["firstName"] = txtFirstName.Text;
            Session["lastName"] = txtLastName.Text;
            Session["payRate"] = txtPayRate.Text;
            Session["startDate"] = txtStartDate.Text;
            Session["endDate"] = txtEndDate.Text;

            Response.Redirect("frmPersonnelVerified.aspx");

        }

这是frmPersonelVerified它从会话中获取变量，在文本框中显示它们，并显示是否写入数据库是否成功。

public partial class frmPersonalVerified : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
    string output = "";

    output += Session["firstName"].ToString() + Environment.NewLine;
    output += Session["lastName"].ToString() + Environment.NewLine;
    output += "Pay Rate: " + Session["payRate"].ToString() + Environment.NewLine;
    output += "Start Date: " + Session["startDate"].ToString() + Environment.NewLine;
    output += "End Date: " + Session["endDate"].ToString() + Environment.NewLine;
    txtVerifiedInfo.Text = output;

    Debug.Assert(Session != null);
    Debug.Assert(Session["txtLastName"] != null);
    Debug.Assert(Session["txtPayRate"] != null);
    Debug.Assert(Session["txtStartDate"] != null);
    Debug.Assert(Session["txtEndDate"] != null);

    // Add your comments here
    if (clsDataLayer.SavePersonnel(Server.MapPath("PayrollSystem_DB.mdb"),
                                   Session["txtFirstName"].ToString(),
                                   Session["txtLastName"].ToString(),
                                   Session["txtPayRate"].ToString(),
                                   Session["txtStartDate"].ToString(),
                                   Session["txtEndDate"].ToString())
                                   )
    {
        txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                              "\nThe information was successfully saved!";

    }
    else
    {
        txtVerifiedInfo.Text = txtVerifiedInfo.Text +
                             "\nThe information was NOT saved.";


    }
}



protected void btnViewPersonnel_Click(object sender, EventArgs e)
{
    Response.Redirect("frmViewPersonnel.aspx");
}


}

Answer 1

您的会话变量不应包含txt前缀。删除它们。使用与您用来设置它们相同的那些。

将数据库作为参数发送时为空引用异常

1 个答案: