如何仅从选定的文本框中更新数据库以获取选择性信息？ （asp.net C＃）

Question

I'm currently coding the SQL for a page to update user details.

How do I code in such a way that the program only updates the textboxes which the user keys information into (meaning to say that user can choose not to fill in all textboxes for update)?

I'm also not sure if I should be using DBnull. Please advise.

Below is my SQL code, and please click here to see my GUI

protected void btnconfirmupdatedetails_Click(object sender, EventArgs e)
{
    string member = (String)Session["ssmem"];
    string strconnect = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString;
    SqlConnection myConnect = new SqlConnection(strconnect);

    string strCommandText = "UPDATE Customer SET Password=@pass, Email=@email, Phone=@phone, Birthdate=@birthday, FirstName=@firstname, LastName=@lastname, Street1=@street1, Street2=@street2, City=@city, State=@state, Postal=@postal ";
    strCommandText+="WHERE Username=@member";

    SqlCommand cmd = new SqlCommand(strCommandText, myConnect);

    cmd.Parameters.Add("@member", SqlDbType.VarChar);
    cmd.Parameters.Add("@pass", SqlDbType.VarChar, 255);
    cmd.Parameters.Add("@email", SqlDbType.VarChar, 200);
    cmd.Parameters.Add("@phone", SqlDbType.VarChar, 50);
    cmd.Parameters.Add("@firstname", SqlDbType.VarChar, 50);
    cmd.Parameters.Add("@lastname", SqlDbType.VarChar, 50);
    cmd.Parameters.Add("@birthday", SqlDbType.Date);
    cmd.Parameters.Add("@street1", SqlDbType.VarChar, 200);
    cmd.Parameters.Add("@street2", SqlDbType.VarChar, 200);
    cmd.Parameters.Add("@city", SqlDbType.VarChar, 50);
    cmd.Parameters.Add("@state", SqlDbType.VarChar, 50);
    cmd.Parameters.Add("@postal", SqlDbType.VarChar, 50);

    cmd.Parameters["@member"].Value = member;

    if (txtPassword.Text == "")
    {
        cmd.Parameters["@pass"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@pass"].Value = txtPassword.Text;
    }//=====

    if (txtEmail.Text == "")
    {
        cmd.Parameters["@email"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@email"].Value = txtEmail.Text;
    }//=====

    if (txtPhoneNumber.Text== "")
    {
        cmd.Parameters["@phone"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@phone"].Value = txtPhoneNumber.Text;
    }//=====

    if (txtFirstName.Text =="")
    {
        cmd.Parameters["@firstname"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@firstname"].Value = txtFirstName.Text;
    }//======

    if (txtBirthday.Text =="")
    {
        cmd.Parameters["@lastname"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@lastname"].Value = txtLastName.Text;
    }//======

    if (txtBirthday.Text =="")
    {
        cmd.Parameters["@birthday"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@birthday"].Value = txtBirthday.Text;
    }//======

    if (txtStreet1.Text =="")
    {
        cmd.Parameters["@street1"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@street1"].Value = txtStreet1.Text;
    }//=======

    if (txtStreet2.Text =="")
    {
        cmd.Parameters["@street2"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@street2"].Value = txtStreet2.Text;
    }//=======

    if (txtCity.Text =="")
    {
        cmd.Parameters["@city"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@city"].Value = txtCity.Text;
    }//========

    if (txtState.Text =="")
    {
        cmd.Parameters["@state"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@state"].Value = txtState.Text;
    }//========

    if (txtPostalCode.Text =="")
    {
        cmd.Parameters["@postal"].Value = DBNull.Value;
    }
    else
    {
        cmd.Parameters["@postal"].Value = txtPostalCode.Text;
    }

    myConnect.Open();

    int result = cmd.ExecuteNonQuery();

    if (result > 0)
    {
        lblErr.Text = "Update successful";
    }
    else
    {
        lblErr.Text = "Update fail";
    }

    myConnect.Close();
}

Answer 1

Try this code snippet. I have used it in stored procedures before and know it works in stored procedures in MSSQL (you did not specify which DB).

UPDATE Customer SET Password=COALESCE(@pass, Password), Email= COALESCE(@email, Email)

Coalesce will return the first parameter with a non-null value. So if you pass null into one of the variables, the coalesce operator will select the value currently stored in the column (the second parameter of the coalesce method).

See here for more information about coalesce.

Answer 2

The most simplest way is- You can load the current data in each textbox at the time of page_load. Later when user wants to change any value, he will do the same and then update all text boxes values.