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update data using oledb in c#

I made a project using c# and data base using access accdb and connected between them both. I made 2 buttons, first one to add new costumer, which works perfectly, and second one to update the data of the costumer (first name and last name), for some reason, the update button does not work, there is no error when I run the project, but after I click nothing happens...
private void button2_Click(object sender, EventArgs e)
{
connect.Open();
string cid = textBox1.Text;
string cfname = textBox2.Text;
string clname = textBox3.Text;
OleDbCommand command = new OleDbCommand();
command.Connection = connect;
command.CommandText = "UPDATE Tcostumers SET cfname= " + cfname + "clname= " + clname + " WHERE cid = " + cid;
if (connect.State == ConnectionState.Open)
{
try
{
command.ExecuteNonQuery();
MessageBox.Show("DATA UPDATED");
connect.Close();
}
catch (Exception expe)
{
MessageBox.Show(expe.Source);
connect.Close();
}
}
else
{
MessageBox.Show("ERROR");
}
}

I believe your commandtext is where the trouble lies;
command.CommandText = "UPDATE Tcostumers SET cfname= " + cfname + "clname= " + clname + " WHERE cid = " + cid;
You require a comma between the set statements, and also as Gino pointed out the speechmarks.
Edit:
It's better than you use parameters for your variables, your current method is open to SQL injection, eg.
private void button2_Click(object sender, EventArgs e)
{
OleDbCommand command = new OleDbCommand(#"UPDATE Tcostumers
SET cfname = #CFName,
clname = #CLName
WHERE cid = #CID", connect);
command.Parameters.AddWithValue("#CFName", textBox2.Text);
command.Parameters.AddWithValue("#CLName", textBox3.Text);
command.Parameters.AddWithValue("#CID", textBox1.Text);
try
{
connect.Open();
}
catch (Exception expe)
{
MessageBox.Show(expe.Source);
}
try
{
command.ExecuteNonQuery();
MessageBox.Show("DATA UPDATED");
}
catch (Exception expe)
{
MessageBox.Show(expe.Source);
}
finally
{
connect.Close();
}
}
Its how I tend to format my code, so do as you will with it. Hope it helps.

It might be a stupid thing but...
you're updating strings not ints so try adding '' to your strings something like:
command.CommandText = "UPDATE Tcostumers SET cfname= '" + cfname + "' clname='" + clname + "' WHERE cid = " + cid;

//my sample code for edit/update
Table Name = StudentFIle
Fields = id,fname,lname
bool found = false;
OleDbConnection BOMHConnection = new OleDbConnection(connect);
string sql = "SELECT * FROM StudentFIle";
BOMHConnection.Open();
OleDbCommand mrNoCommand = new OleDbCommand(sql, BOMHConnection);
OleDbDataReader mrNoReader = mrNoCommand.ExecuteReader();
while (mrNoReader.Read())
{
if (mrNoReader["id"].ToString().ToUpper().Trim() == idtextbox.Text.Trim())
{
mrNoReader.Close();
string query = "UPDATE StudentFIle set fname='" +firstnametextbox.Text+ "',lname='"+lastnametextbox.Text+"' where id="+idtextbox.Text+" ";
mrNoCommand.CommandText = query;
mrNoCommand.ExecuteNonQuery();
MessageBox.Show("Successfully Updated");
found = true;
break;
}
continue;
}
if (found == false)
{
MessageBox.Show("Id Doesn't Exist !.. ");
mrNoReader.Close();
BOMHConnection.Close();
idtextbox.Focus();
}

Error by this code

When I fill out the form and click registration, it shows an error:
Object reference not set to an instance of an object.
The error is here:
int temp=Convert.ToInt32(com.ExecuteScalar().ToString());
Which object must be added to refrence?
Here is the code of the web page:
public partial class register : System.Web.UI.Page
{
protected void Page_Load(object sender, EventArgs e)
{
Page.DataBind();
if(IsPostBack)
{
SqlConnection conn = new
SqlConnection(ConfigurationManager.ConnectionStrings["RegistrationConnectionS
tring"].ConnectionString);
conn.Open();
string checkuser = "SELECT * FROM [Table] where user_name ='" +
Text_username + "'";
SqlCommand com = new SqlCommand (checkuser , conn);
int temp=Convert.ToInt32(com.ExecuteScalar().ToString());
if (temp == 1){
Response.Write("User already exists");
}
conn.Close();
}
}
protected void Button2_Click(object sender, EventArgs e)
{
Text_fname.Text = "";
Text_lname.Text = "";
Text_email.Text = "";
Text_password.Text = "";
Text_password_again.Text = "";
Text_username.Text = "";
}
protected void Button1_Click(object sender, EventArgs e)
{
try
{
SqlConnection conn = new
SqlConnection(ConfigurationManager.ConnectionStrings["RegistrationConnectionS
tring"].ConnectionString);
conn.Open();
string insert = "insert into Table
(user_fname,user_lname,user_email,user_password,user_name) values (#firstName
,#lastName ,#Email ,#passWord ,#userName)";
SqlCommand com = new SqlCommand (insert , conn);
com.Parameters.AddWithValue("#firstName", Text_fname.Text);
com.Parameters.AddWithValue("#lastName", Text_lname.Text);
com.Parameters.AddWithValue("#Email", Text_email.Text);
com.Parameters.AddWithValue("#passWord", Text_password.Text);
com.Parameters.AddWithValue("#userName", Text_username.Text);
com.ExecuteNonQuery();
Response.Write("Registration is successful");
Response.Redirect("Default.aspx");
conn.Close();
}
catch (Exception ex)
{
Response.Write("Error: " + ex.ToString());
}
}
}

From the error message you have posted, it is clear that the com.ExecuteScalar() is null. Hence, when you call the ToString method on it you get a null reference exception. Since the com.ExecuteScalar() can be null, I suggest you do a check for this.
int temp;
var result = com.ExecuteScalar();
if(result != null)
{
temp = Convert.ToInt32(result.ToString());
}
if (temp == 1)
{
Response.Write("User already exists");
}

can not Update data in C# Database Access

I have a problem with the button3 it's the UPDATE BUTTON, The message box keeps saying it's a syntax error in the UPDATE Statement. And also if I create another listbox, if I insert a new data, it does not make me insert another data in the 2nd listbox. So if I insert something on the 1st listbox, that index would, for example, be 9, then I would try to insert on the next listbox, but then it would proceed to the index 10.
OleDbCommand cmd = new OleDbCommand();
OleDbConnection cn = new OleDbConnection();
OleDbDataReader dr;
private void listBox2_Click(object sender, EventArgs e)
{
ListBox l = sender as ListBox;
if (l.SelectedIndex != 1)
{
listBox1.SelectedIndex = l.SelectedIndex;
listBox2.SelectedIndex = l.SelectedIndex;
textBox2.Text = listBox2.SelectedItem.ToString();
}
}
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text != "")
{
string q = "insert into Table1 (name) values ('"+textBox1.Text.ToString()+"')";
doSomething(q);
textBox1.Text = null;
}
}
private void button2_Click(object sender, EventArgs e)
{
if (listBox1.SelectedIndex != -1)
{
string q = "delete from Table1 where id=" + listBox1.SelectedItem.ToString();
doSomething(q);
}
}
private void button3_Click(object sender, EventArgs e)
{
if (textBox2.Text != "" & listBox1.SelectedIndex != -1)
{
string q = "update Table1 set (name) '" + textBox2.Text.ToString() + "' where id " + listBox1.SelectedItem.ToString();
doSomething(q);
textBox2.Text = "";
}
}
private void doSomething(String q)
{
try
{
cn.Open();
cmd.CommandText = q;
cmd.ExecuteNonQuery();
cn.Close();
loaddata();
}
catch (Exception e)
{
cn.Close();
MessageBox.Show(e.Message.ToString());
}
}

Problem 1: you are missing = Symbol while providing input parameters.
Try This:
string q = "update Table1 set [name]= '" + textBox2.Text.ToString() + "' where id= " + listBox1.SelectedItem.ToString();
Problem 2: you are not assigning connection object to `OleDbCommand.
Add This: before executing command
cmd.Connection=cn;
Complete Code:
OleDbCommand cmd = new OleDbCommand();
OleDbConnection cn = new OleDbConnection();
OleDbDataReader dr;
private void listBox2_Click(object sender, EventArgs e)
{
ListBox l = sender as ListBox;
if(l.SelectedIndex!=-1)
textBox2.Text = l.SelectedItem.ToString();
}
}
private void button1_Click(object sender, EventArgs e)
{
if (textBox1.Text != "")
{
string q = "insert into Table1(name) values ('"+textBox1.Text.ToString()+"')";
doSomething(q);
textBox1.Text = null;
}
}
private void button2_Click(object sender, EventArgs e)
{
if (listBox1.SelectedIndex != -1)
{
string q = "delete from Table1 where id=" + listBox1.SelectedItem.ToString();
doSomething(q);
}
}
private void button3_Click(object sender, EventArgs e)
{
if (textBox2.Text != "" & listBox1.SelectedIndex != -1)
{
string q = "update Table1 set [name] ='" + textBox2.Text.ToString() + "' where id =" + listBox1.SelectedItem.ToString();
doSomething(q);
textBox2.Text = "";
}
}
private void doSomething(String q)
{
try
{
cn.Open();
cmd.CommandText = q;
cmd.Connection=cn;
cmd.ExecuteNonQuery();
cn.Close();
loaddata();
}
catch (Exception e)
{
cn.Close();
MessageBox.Show(e.Message.ToString());
}
}
Suggestion : your query is open to SQL injection attacks , i would suggest to use Parameterised Queries to avoid them.
Using Parameterised Queries :
private void doSomething(String q)
{
try
{
cn.Open();
cmd.CommandText = "update Table1 set [name]=#name where id=#id";
cmd.Parameters.AddWithValue("#name",textBox2.Text.ToString());
cmd.Parameters.AddWithValue("#id",listBox1.SelectedItem.ToString());
cmd.ExecuteNonQuery();
cn.Close();
loaddata();
}
catch (Exception e)
{
cn.Close();
MessageBox.Show(e.Message.ToString());
}
}

string q = "update Table1 set (name) '" + textBox2.Text.ToString() + "' where id " + listBox1.SelectedItem.ToString();
In the above code (btn3) your are missing id =
Write code like this :
string q = "update Table1 set (name) '" + textBox2.Text.ToString() + "' where id=" + listBox1.SelectedItem.ToString();
UPDATE :
My Access query function:
public void ExecuteAccessQurey(string _pQurey)
{
OleDbConnection con = new OleDbConnection("DatabaseConnectionString");
OleDbCommand cmd = new OleDbCommand(_pQurey, con);
if (con.State == System.Data.ConnectionState.Closed)
{
con.Open();
}
cmd.ExecuteNonQuery();
con.Close();
}

How to get next data row by hiting on Next button

I want to get next record from table to show as Question. With below code I am not able to get next Question from table.
protected void Page_Load(object sender, EventArgs e)
{
if (Page.IsPostBack == false)
{
Quiz_Load();
}
}
private void Quiz_Load()
{
try
{
if (Session["UserQuizID"] != null)
{
string mayank = "mm.bhagat";
string UserQuiz_ID = Session["UserQuizID"].ToString();
SqlConnection con = new SqlConnection(c);
SqlCommand cmd = new SqlCommand("select top 0.1 percent QuestionID, Title, Answer1,Answer2,Answer3,Answer4,UserAnswer from [Table_UserAnswer] WHERE UserQuizID = '" + UserQuiz_ID.ToString() + "' AND UserName = '" + mayank.ToString() + "' order by newid()", con);
con.Open();
SqlDataReader dr = cmd.ExecuteReader();
if (dr.Read())
{
Session["QuestionID"] = dr[0].ToString();
Lbl_QuestionTitle.Text = dr[1].ToString();
RadBut_Answer.Items.Add(dr[2].ToString());
RadBut_Answer.Items.Add(dr[3].ToString());
RadBut_Answer.Items.Add(dr[4].ToString());
RadBut_Answer.Items.Add(dr[5].ToString());
Session["UserAnswer"] = dr[6].ToString();
}
else
{
}
con.Close();
}
else
{
Response.Redirect("Start.aspx");
}
}
catch
{
}
}
protected void RadBut_Answer_SelectedIndexChanged(object sender, EventArgs e)
{
try
{
int getvalue;
getvalue = Convert.ToInt32(RadBut_Answer.SelectedIndex + 1);
Lbl_SelectedAnsMsg.Text = MessageFormatter.GetFormattedAlertsMessage("Your Selected Answer is : " + getvalue.ToString());
Session["UserAnswer"] = getvalue.ToString();
}
catch
{
}
}
protected void But_Next_Click(object sender, EventArgs e)
{
UpdateUserAns();
if (Session["UserAnswer"] == null)
{
Response.Redirect("Result.aspx");
}
else
{
}
}
private void UpdateUserAns()
{
try
{
string mayank = "mm.bhagat";
string UserQuiz_ID = Session["UserQuizID"].ToString();
string Question_ID = Session["QuestionID"].ToString();
string User_Answer = Session["UserAnswer"].ToString();
SqlConnection con = new SqlConnection(c);
SqlCommand cmd = new SqlCommand("UPDATE Table_UserAnswer SET UserAnswer='" + User_Answer.ToString() + "' WHERE UserQuizID = '"+ UserQuiz_ID.ToString() +"' AND QuestionID = '"+Question_ID.ToString()+"' AND UserName = '"+mayank.ToString()+"'", con);
con.Open();
cmd.ExecuteNonQuery();
con.Close();
cmd.Cancel();
}
catch
{
}
}

hi check this post client here
here you can find solution of your question

Updating Database Using Datagridview

I can add, edit, delete database using listbox. But I want to do it using DatagridView I already bind it to my database.
How do I add,edit,delete update my database in datagridview using codes?
These are my codes:
namespace Icabales.Homer
{
public partial class Form1 : Form
{
SqlConnection cn = new SqlConnection(#"Data Source=.\SQLEXPRESS;AttachDbFilename=c:\users\homer\documents\visual studio 2010\Projects\Icabales.Homer\Icabales.Homer\Database1.mdf;Integrated Security=True;User Instance=True");
SqlCommand cmd = new SqlCommand();
SqlDataReader dr;
SqlDataAdapter da;
DataTable dt = new DataTable();
public Form1()
{
InitializeComponent();
}
private void bindgrid()
{
string command = "select * from info";
da = new SqlDataAdapter(command, cn);
da.Fill(dt);
dataGridView1.DataSource = dt;
}
private void Form1_Load(object sender, EventArgs e)
{
// TODO: This line of code loads data into the 'database1DataSet.info' table. You can move, or remove it, as needed.
this.infoTableAdapter.Fill(this.database1DataSet.info);
cmd.Connection = cn;
loadlist();
bindgrid();
}
private void button1_Click(object sender, EventArgs e)
{
if (txtid.Text != "" & txtname.Text != "")
{
cn.Open();
cmd.CommandText = "insert into info (id,name) values ('" + txtid.Text + "' , '" + txtname.Text + "')";
cmd.ExecuteNonQuery();
cmd.Clone();
MessageBox.Show("Record Inserted");
cn.Close();
txtid.Text = "";
txtname.Text = "";
loadlist();
}
}
private void loadlist()
{
listBox1.Items.Clear();
listBox2.Items.Clear();
cn.Open();
cmd.CommandText = "select * from info";
dr = cmd.ExecuteReader();
if (dr.HasRows)
{
while (dr.Read())
{
listBox1.Items.Add(dr[0].ToString());
listBox2.Items.Add(dr[1].ToString());
}
}
cn.Close();
}
private void listBox2_SelectedIndexChanged(object sender, EventArgs e)
{
ListBox l = sender as ListBox;
if (l.SelectedIndex != -1)
{
listBox1.SelectedIndex = l.SelectedIndex;
listBox2.SelectedIndex = l.SelectedIndex;
txtid.Text = listBox1.SelectedItem.ToString();
txtname.Text = listBox2.SelectedItem.ToString();
}
}
private void button2_Click(object sender, EventArgs e)
{
if (txtid.Text != "" & txtname.Text != "")
{
cn.Open();
cmd.CommandText = "delete from info where id = '"+txtid.Text+"'and name = '"+txtname.Text+"'";
cmd.ExecuteNonQuery();
cn.Close();
MessageBox.Show("Record Deleted");
loadlist();
txtid.Text = "";
txtname.Text = "";
}
}
private void button3_Click(object sender, EventArgs e)
{
if (txtid.Text != "" & txtname.Text != "" & listBox1.SelectedIndex != -1)
{
cn.Open();
cmd.CommandText = "update info set id='"+txtid.Text+"',name='"+txtname.Text+"'where id='"+listBox1.SelectedItem.ToString()+"' and name='"+listBox2.SelectedItem.ToString()+"'";
cmd.ExecuteNonQuery();
cn.Close();
MessageBox.Show("Record Updated");
loadlist();
txtid.Text = "";
txtname.Text = "";
}
}
}
}

I have a dataGridView and a button on a form. When I do any editing, insertion or deletion in the dataGridView1, the code below does the magic
public partial class EditPermit : Form
{
OleDbCommand command;
OleDbDataAdapter da;
private BindingSource bindingSource = null;
private OleDbCommandBuilder oleCommandBuilder = null;
DataTable dataTable = new DataTable();
public EditPermit()
{
InitializeComponent();
}
private void EditPermitPermit_Load(object sender, EventArgs e)
{
DataBind();
}
private void btnSv_Click(object sender, EventArgs e)
{
dataGridView1.EndEdit(); //very important step
da.Update(dataTable);
MessageBox.Show("Updated");
DataBind();
}
private void DataBind()
{
dataGridView1.DataSource = null;
dataTable.Clear();
String connectionString = MainWindow.GetConnectionString(); //use your connection string please
String queryString1 = "SELECT * FROM TblPermitType"; // Use your table please
OleDbConnection connection = new OleDbConnection(connectionString);
connection.Open();
OleDbCommand command = connection.CreateCommand();
command.CommandText = queryString1;
try
{
da = new OleDbDataAdapter(queryString1, connection);
oleCommandBuilder = new OleDbCommandBuilder(da);
da.Fill(dataTable);
bindingSource = new BindingSource { DataSource = dataTable };
dataGridView1.DataSource = bindingSource;
}
catch (Exception ex)
{
MessageBox.Show(ex.ToString(), "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
}
}

I have implemented a solution that inserts/updates/deletes data in MS SQL database directly from DataGridView.
To accomplish this I have used the following events: RowValidating and UserDeletingRow.
It is supposed that you have
SqlConnection _conn;
declared and initialized.
Here is the code:
private void dgv_RowValidating( object sender, DataGridViewCellCancelEventArgs e )
{
try
{
if (!dgv.IsCurrentRowDirty)
return;
string query = GetInsertOrUpdateSql(e);
if (_conn.State != ConnectionState.Open)
_conn.Open();
var cmd = new SqlCommand( query, _conn );
cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
MessageBox.Show( ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning );
}
}
public string GetInsertOrUpdateSql( DataGridViewCellCancelEventArgs e )
{
DataGridViewRow row = dgv.Rows[e.RowIndex];
int id = 0;
int.TryParse( row.Cells["Id"].Value.ToString(), out id );
DateTime dob;
DateTime.TryParse( row.Cells["Dob"].Value.ToString(), out dob );
string email = row.Cells["Email"].Value.ToString();
string phone = row.Cells["Phone"].Value.ToString();
string fio = row.Cells["Fio"].Value.ToString();
if (id == 0)
return string.Format( "insert into {0} Values ('{1}','{2}','{3}','{4}')", "dbo.People", fio, dob.ToString( "dd-MM-yyyy" ), email, phone );
else
return string.Format( "update {0} set Fio='{1}', Dob='{2}', Email='{3}', Phone='{4}' WHERE Id={5}", "dbo.People", fio, dob.ToString( "dd-MM-yyyy" ), email, phone, id );
}
private void dgv_UserDeletingRow( object sender, DataGridViewRowCancelEventArgs e )
{
try
{
int id = 0;
int.TryParse( e.Row.Cells["Id"].Value.ToString(), out id );
string query = string.Format( "DELETE FROM {0} WHERE Id = {1}", "dbo.People", id );
var cmd = new SqlCommand( query, _conn );
if (_conn.State != ConnectionState.Open)
_conn.Open();
cmd.ExecuteNonQuery();
}
catch (Exception ex)
{
MessageBox.Show( ex.Message, "Error", MessageBoxButtons.OK, MessageBoxIcon.Warning );
}
}
Hope this helps.

I have the same kind of project at home, I do not have the source code with me but if needed I can check somewhere this weekend to see what exactly I have done, but I believe it's some of the following:
Since you are using a dataset and a dataadapter this can be achieved very easily.
As long as your DataGridView1 has the properties enabled for users to add/delete/edit rows you could use the following code.
DataAdapter.Update(DataTable);
//in your code this would be:
da.Update(dt);
The DataAdapter.Update() Method will auto generate any insert/update/delete commands needed to update the results of your fill query compared with the current data in your datagridview.
You can set those commands (properties) as well in case you prefer to modify them, though this is not necessary.
This only works ofcourse after a user has made changes to the DataGridView. Add this code to a simple button and see if you have any luck. It definitly was something this simple :)