如何使用自动递增键更新update语句的并发问题？

Question

I have run into the following error message at run-time with my novice's Sql / Visual C# database program:

Concurrency violation: the UpdateCommand affected 0 of the expected 1 records.

I have done some searching around about this issue and have seen several threads about it, but they aren't enough for me to resolve the issue. I noticed people talking about how it can often occur when you're using an auto-incrementing primary key. That is the case in this program. Also there is no multithreading or anything else like that that I am coding into this program. Therefore I think the auto-increment is possibly the only problem.

That being said, how do I get the update command to work, despite the auto-increment? I can hardly stand on two feet when it comes to database programming, so please be detailed, if you don't mind. Also the command I'm using is via a SqlCommandBuilder object. I have set that object to new SqlCommandBuilder(DataAdapter), and I have not done anything special with it.

Thanks.

---

This edit is the second one. The first one is below.

Due to my inexperience with database programming, I am unable to say this for sure. However I have good reason to believe that the problem I am experiencing has to do with new rows not getting added to the database completely until the program terminates. I do not understand why they are waiting until program termination to do that, or if they are waiting until then, just what exactly what about the program's termination causes them to suddenly get saved completely. However I have forgotten to mention that this error only occurs on rows that I have added during that specific execution of the program. If the row was already added on a previous execution or through pre-existing table data, everything's fine. I am getting the same error with the delete method, and it also only occurs with new rows.

How do I get these rows to be fully saved to everything so that this doesn't happen? What about the program's termination is causing these rows to get fully saved? Thanks!

---

Due to a request, I have left here two code snippets. The first one will be the method in which the the problem occurs. The next one will include the entire class. There are only two classes in the entire program, and the other class doesn't seem important to me in this particular issue.

    private void btnUpdate_Click(object sender, EventArgs e)
    {
        if (recordShown)
        {
            con.Open();

            currentRow[1] = tbFirstName.Text;
            currentRow[2] = tbMiddleName.Text;
            currentRow[3] = tbLastName.Text;
            currentRow[4] = tbSuffix.Text;
            currentRow[5] = tbHomePhone.Text;
            currentRow[6] = tbCellPhone.Text;
            currentRow[7] = tbOtherPhone.Text;
            currentRow[8] = tbStreetAddress.Text;
            currentRow[9] = tbCityAndState.Text;
            currentRow[10] = tbCountry.Text;
            currentRow[11] = tbEmail.Text;

            dAdapter.Update(dataset, "Contacts");

            con.Close();
        }
        else
        {
            MessageBox.Show("Please locate/add a record first.");
        }
    }

Next snippet:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Dakota
{
public partial class Form1 : Form
{
    SqlConnection con;
    DataSet dataset;
    SqlDataAdapter dAdapter;
    DataRow currentRow;
    string primaryKey;
    SqlCommandBuilder cmdBuilder;
    bool recordShown = false;

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        dataset = new DataSet();
        con = new SqlConnection();

        con.ConnectionString = "Data Source=.\\SQLEXPRESS;" +
            "AttachDbFilename=C:\\Users\\Sterling\\Documents\\Contacts.mdf;" +
            "Integrated Security=True;Connect Timeout=30;User Instance=True";

        con.Open();

        string getData = "SELECT * FROM tblContacts";
        dAdapter = new SqlDataAdapter(getData, con);
        dAdapter.Fill(dataset, "Contacts");
        cmdBuilder = new SqlCommandBuilder(dAdapter);
        cmdBuilder.ConflictOption = ConflictOption.OverwriteChanges;

        con.Close();
    }

    private void clearTextBoxes()
    {
        tbFirstName.Clear();
        tbMiddleName.Clear();
        tbLastName.Clear();
        tbSuffix.Clear();
        tbHomePhone.Clear();
        tbCellPhone.Clear();
        tbOtherPhone.Clear();
        tbStreetAddress.Clear();
        tbCityAndState.Clear();
        tbCountry.Clear();
        tbEmail.Clear();
    }

    private void fillTextBoxes(int row)
    {
        DataRow dr = dataset.Tables["Contacts"].Rows[row];
        tbFirstName.Text = dr.ItemArray.GetValue(1).ToString();
        tbMiddleName.Text = dr.ItemArray.GetValue(2).ToString();
        tbLastName.Text = dr.ItemArray.GetValue(3).ToString();
        tbSuffix.Text = dr.ItemArray.GetValue(4).ToString();
        tbHomePhone.Text = dr.ItemArray.GetValue(5).ToString();
        tbCellPhone.Text = dr.ItemArray.GetValue(6).ToString();
        tbOtherPhone.Text = dr.ItemArray.GetValue(7).ToString();
        tbStreetAddress.Text = dr.ItemArray.GetValue(8).ToString();
        tbCityAndState.Text = dr.ItemArray.GetValue(9).ToString();
        tbCountry.Text = dr.ItemArray.GetValue(10).ToString();
        tbEmail.Text = dr.ItemArray.GetValue(11).ToString();
    }

    private void fillTextBoxes(DataRow dr)
    {
        tbFirstName.Text = dr.ItemArray.GetValue(1).ToString();
        tbMiddleName.Text = dr.ItemArray.GetValue(2).ToString();
        tbLastName.Text = dr.ItemArray.GetValue(3).ToString();
        tbSuffix.Text = dr.ItemArray.GetValue(4).ToString();
        tbHomePhone.Text = dr.ItemArray.GetValue(5).ToString();
        tbCellPhone.Text = dr.ItemArray.GetValue(6).ToString();
        tbOtherPhone.Text = dr.ItemArray.GetValue(7).ToString();
        tbStreetAddress.Text = dr.ItemArray.GetValue(8).ToString();
        tbCityAndState.Text = dr.ItemArray.GetValue(9).ToString();
        tbCountry.Text = dr.ItemArray.GetValue(10).ToString();
        tbEmail.Text = dr.ItemArray.GetValue(11).ToString();
    }

    private void btnSearch_Click(object sender, EventArgs e)
    {
        string searchFor = tbSearchFor.Text;
        string column;
        if (rbFirstName.Checked)
        {
            column = "firstName";
        }
        else
        {
            column = "lastName";
        }

        DataRow[] rows = dataset.Tables["Contacts"].Select(column + "='" + searchFor + "'");
        int number = rows.Length;

        if (number == 0)
        {
            MessageBox.Show("No such records were found.");
        }
        else if (number > 1)
        {
            string[] strings = new string[rows.Length];
            for (int i = 0; i < strings.Length; i++)
            {
                bool hasFirst = false;
                bool hasMiddle = false;

                strings[i] = "";
                if (rows[i].ItemArray.GetValue(1).ToString() != "")
                {
                    hasFirst = true;
                    strings[i] += rows[i].ItemArray.GetValue(1).ToString();
                }
                if (rows[i].ItemArray.GetValue(2).ToString() != "")
                {
                    hasMiddle = true;
                    if (hasFirst)
                    {
                        strings[i] += " ";
                    }
                    strings[i] += rows[i].ItemArray.GetValue(2).ToString();
                }
                if (rows[i].ItemArray.GetValue(3).ToString() != "")
                {
                    if ((hasFirst && !hasMiddle) || (hasMiddle))
                    {
                        strings[i] += " ";
                    }
                    strings[i] += rows[i].ItemArray.GetValue(3).ToString();
                }
                if (rows[i].ItemArray.GetValue(4).ToString() != "")
                {
                    strings[i] += " " + rows[i].ItemArray.GetValue(4).ToString();
                }
            }

           // int choice;
            Form2 form2 = new Form2(strings);
            if (form2.ShowDialog(this) == DialogResult.OK)
            {
                primaryKey = rows[form2.choice].ItemArray.GetValue(0).ToString();
               // choice = form2.choice;
                fillTextBoxes(rows[form2.choice]);
                currentRow = rows[form2.choice];
                recordShown = true;
            }
        }            
        else
        {
            primaryKey = rows[0].ItemArray.GetValue(0).ToString();
            currentRow = rows[0];
            fillTextBoxes(rows[0]);
            recordShown = true;
        }
    }

    private void btnAdd_Click(object sender, EventArgs e)
    {
        con.Open();

        DataRow row = dataset.Tables["Contacts"].NewRow();
        row[1] = tbFirstName.Text;
        row[2] = tbMiddleName.Text;
        row[3] = tbLastName.Text;
        row[4] = tbSuffix.Text;
        row[5] = tbHomePhone.Text;
        row[6] = tbCellPhone.Text;
        row[7] = tbOtherPhone.Text;
        row[8] = tbStreetAddress.Text;
        row[9] = tbCityAndState.Text;
        row[10] = tbCountry.Text;
        row[11] = tbEmail.Text;
        currentRow = row;

        dataset.Tables["Contacts"].Rows.Add(row);
        dAdapter.Update(dataset, "Contacts");
        recordShown = true;

        con.Close();
    }

    private void btnUpdate_Click(object sender, EventArgs e)
    {
        if (recordShown)
        {
            con.Open();

            currentRow[1] = tbFirstName.Text;
            currentRow[2] = tbMiddleName.Text;
            currentRow[3] = tbLastName.Text;
            currentRow[4] = tbSuffix.Text;
            currentRow[5] = tbHomePhone.Text;
            currentRow[6] = tbCellPhone.Text;
            currentRow[7] = tbOtherPhone.Text;
            currentRow[8] = tbStreetAddress.Text;
            currentRow[9] = tbCityAndState.Text;
            currentRow[10] = tbCountry.Text;
            currentRow[11] = tbEmail.Text;

            dAdapter.Update(dataset, "Contacts");

            con.Close();
        }
        else
        {
            MessageBox.Show("Please locate/add a record first.");
        }
    }

    private void btnDelete_Click(object sender, EventArgs e)
    {
        con.Open();

        currentRow.Delete();
        dAdapter.Update(dataset, "Contacts");
        clearTextBoxes();
        recordShown = false;

        con.Close();
    }
}
}

Thanks!

Answer 1

Here is one explanation but I am not sure if it is exactly what you are seeing:

http://blogs.msdn.com/b/spike/archive/2010/04/07/concurrency-violation-the-updatecommand-affected-0-of-the-expected-1-records.aspx

This might be more on track and if so points to some missing lines that should come after you declare cmdBuilder:

dAdapter.UpdateCommand = cmdBuilder.GetUpdateCommand();
dAdapter.InsertCommand = cmdBuilder.GetInsertCommand();
dAdapter.DeleteCommand = cmdBuilder.GetDeleteCommand();

http://www.codeguru.com/forum/archive/index.php/t-337168.html

Also, you might need to call:

dAdapter.Fill(dataset, "Contacts");

before the con.Close() for all three operations (Insert, Update, and Delete).


On an unrelated note, you could reduce duplicate code by changing the "fillTextBoxes(int row)" method to be just:

private void fillTextBoxes(int row)
{
  DataRow dr = dataset.Tables["Contacts"].Rows[row];
  fillTextBoxes(dr);
}

Answer 2

A couple things, it looks like you are not passing it back the ID of your identity column when calling update. Wouldn't it need to know the ID when doing an update?

In addition to the comment that srutzky made about the redundant code in fillTextBoxes, you might also consider not referencing your columns by ordinal value and instead reference them by their actual column name. If you were to add a column to your DB, it would break all of your code that is doing things like:

tbLastName.Text = dr.ItemArray.GetValue(3).ToString();

Instead, you might do something like:

tbLastName.Text = dr.ItemArray.GetValue("LastName").ToString();

I don't know offhand if GetValue takes the column name as a parameter, but I'm sure it is something like that.