Question

网页更新数据库，但如果我没有写任何东西，他会删除数据库中的数据，如何检查代码中是否有更新

protected void btnsave_Click(object sender, EventArgs e)
{
    using (DataClasses1DataContext sdc = new DataClasses1DataContext()) {      
        string fileName = FileUpload1.FileName;
        byte[] fileByte = FileUpload1.FileBytes;
        Binary binaryObj = new Binary(fileByte);
        Professor_Dim prof = sdc.Professor_Dims.SingleOrDefault(x => x.P_ID == 0);
        prof.P_Fname = txtfirstname.Text;
        prof.P_Lname = txtlastname.Text;
        prof.P_Email = txtemail.Text;
        prof.P_Address = txtaddress.Text;
        prof.P_Phone = txtphone.Text;
        prof.P_Image = binaryObj;
        sdc.SubmitChanges();
    }
}

Answer 1

protected void btnsave_Click(object sender, EventArgs e)
{
    using (DataClasses1DataContext sdc = new DataClasses1DataContext()) 
    {      
        string fileName = FileUpload1.FileName;
        byte[] fileByte = FileUpload1.FileBytes;
        Binary binaryObj = new Binary(fileByte);
        Professor_Dim prof = sdc.Professor_Dims.SingleOrDefault(x => x.P_ID == 0);

        if (  !string.IsNullOrEmpty(txtfirstname.Text))
            prof.P_Fname = txtfirstname.Text;

        if (  !string.IsNullOrEmpty(txtlastname.Text))
            prof.P_Lname = txtlastname.Text;

        if (  !string.IsNullOrEmpty(txtemail.Text))
            prof.P_Email = txtemail.Text;

        if (  !string.IsNullOrEmpty(txtaddress.Text))
            prof.P_Address = txtaddress.Text;

        if (  !string.IsNullOrEmpty(txtphone.Text))
            prof.P_Phone = txtphone.Text;

        prof.P_Image = binaryObj;
        sdc.SubmitChanges();
    }
}

Answer 2

您想使用GetChangeSet（）

ChangeSet cs = sdc.GetChangeSet();

https://msdn.microsoft.com/en-us/library/system.data.linq.datacontext.getchangeset(v=vs.110).aspx

这将为您提供一个包含三个成员的对象，一个已更改行的列表，一个已删除行列表以及一个已插入行列表。

检查是否有更新

2 个答案: