我想只更新数据库中启用了文本框的那些列，并保留以前禁用的数据？

Question

（http://s14.directupload.net/images/140127/fooispgt.jpg）图片链接

请查看图片以获得更多关于问题的说明bcz我知道我无法让您更清楚。

我想只更新那些由用户通过复选框检查的列的数据，而那些未经检查的列不会被NULL值更新....

我在想的是使用511 if .... else为不同的更新查询条件，但是不可能实现它。

到目前为止，更新代码是：

else if(update_rdbtn.Checked)
            {

                FileStream fstream = new FileStream(this.imglocation_lbl.Text, FileMode.Open, FileAccess.Read);
                BinaryReader br = new BinaryReader(fstream);
                imgbtarray = br.ReadBytes((int)fstream.Length);
                SqlConnection con = new SqlConnection("Data Source=JackSparrow-PC\\sqlexpress;Initial Catalog=HCE_DB;Integrated Security=True;Pooling=False");

                SqlCommand cmd = new SqlCommand("Update StudentInfo SET Rollno='" + this.rollno_txtbox.Text + "',Student_Name='" + this.studname_txtbox.Text + "',F_name='" + this.fname_txtbox.Text + "',D_O_B='" + this.dob_txtbox.Text + "',Address='" + this.address_txtbox.Text + "',Phone='" + this.phone_txtbox.Text + "',Valid_upto='" + this.validupto_txtbox.Text + "',Image=@IMG,Branch='" + this.branch_txtbox.Text + "' WHERE Rollno='" + this.rollno_txtbox.Text + "';", con);
                SqlDataReader myReader;
            try
            {
                con.Open();
                cmd.Parameters.Add(new SqlParameter("@IMG", imgbtarray));
                myReader = cmd.ExecuteReader();
                MessageBox.Show("Data has been updated");
                myReader.Close();
                con.Close();
            }

            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }

已检查的电台btn代码已更改：

   private void update_rdbtn_CheckedChanged(object sender, EventArgs e)
    {
        update_grpbox.Enabled = true;
        studname_txtbox.Enabled = false;
        fname_txtbox.Enabled = false;
        dob_txtbox.Enabled = false;
        branch_txtbox.Enabled = false;
        address_txtbox.Enabled = false;
        phone_txtbox.Enabled = false;
        validupto_txtbox.Enabled = false;
        Browse_btn.Enabled = false;
        studname_chkbox.Checked = false;
        fname_chkbox.Checked = false;
        dob_chkbox.Checked = false;
        branch_chkbox.Checked = false;
        Address_chkbox.Checked = false;
        phone_chkbox.Checked = false;
        validupto_chkbox.Checked = false;
        Uploadimg_chkbox.Checked = false;
    }

复选框代码：

 private void studname_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!studname_chkbox.Checked)
        {
            studname_txtbox.Enabled = false;
        }
        else
        {
            studname_txtbox.Enabled = true;
        }
    }

    private void fname_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!fname_chkbox.Checked)
        {
            fname_txtbox.Enabled = false;
        }
        else
        {
            fname_txtbox.Enabled = true;
        }
    }

    private void dob_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!dob_chkbox.Checked)
        {
            dob_txtbox.Enabled = false;
        }
        else
        {
            dob_txtbox.Enabled = true;
        }
    }

    private void branch_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!branch_chkbox.Checked)
        {
            branch_txtbox.Enabled = false;
        }
        else
        {
            branch_txtbox.Enabled = true;
        }
    }

    private void Address_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!Address_chkbox.Checked)
        {
            address_txtbox.Enabled = false;
        }
        else
        {
            address_txtbox.Enabled = true;
        }
    }

    private void phone_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!phone_chkbox.Checked)
        {
            phone_txtbox.Enabled = false;
        }
        else
        {
            phone_txtbox.Enabled = true;
        }
    }

    private void validupto_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!validupto_chkbox.Checked)
        {
            validupto_txtbox.Enabled = false;
        }
        else
        {
            validupto_txtbox.Enabled = true;
        }
    }

    private void Uploadimg_chkbox_CheckedChanged(object sender, EventArgs e)
    {
        if (!Uploadimg_chkbox.Checked)
        {
            Browse_btn.Enabled = false;
        }
        else
        {
            Browse_btn.Enabled = true;
        }
    }