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why i get this error when i do allow paging True The data source does not support server-side data paging

I had opened a related topic before, but I realized the problem now. When I set allow paging correctly in the properties of gridview in web form.aspx, I get this error. I don't know if the codes I wrote in aspx.cs browser cause this problem, please help
'''
public partial class WebForm1 : System.Web.UI.Page
{
SqlConnection con = new SqlConnection("Data Source=MERIH-PC;Initial Catalog=aspidus;Integrated Security=True");
protected void Page_Load(object sender, EventArgs e)
{
if (!IsPostBack)
{
GVbind();
}
}
void clear()
{
txtName.Text = "";
txtPhone.Text = "";
txtAdd.Text = "";
}
protected void btnInsert_Click(object sender, EventArgs e)
{
con.Open();
SqlCommand cmd = new SqlCommand(#"INSERT INTO [dbo].[idus] VALUES ('" + txtName.Text + "', '" + txtPhone.Text + "', '" + txtAdd.Text + "')", con);
int t = cmd.ExecuteNonQuery();
if (t > 0)
{
Response.Write("<script>alert('Data inserted successfully') </script>");
con.Close();
}
GVbind();
clear();
}
//protected void btnDelete_Click(object sender, EventArgs e)
//{
// SqlCommand cmd = new SqlCommand(#"DELETE FROM [dbo].[idus]
// WHERE [ID]='" + txtID.Text + "'", con);
// con.Open();
// cmd.ExecuteNonQuery();
// Response.Write("Data deleted successfully");
// con.Close();
//}
//protected void btnUpdate_Click(object sender, EventArgs e)
//{
// SqlCommand cmd = new SqlCommand(#"UPDATE [dbo].[idus]
// SET[ID] = '" + txtID.Text + "',[name] = '" + txtName.Text + "',[phone] = '" + txtPhone.Text + "',[address] = '" + txtAdd.Text + "' WHERE [ID]= '" + txtID.Text + "'", con);
// con.Open();
// cmd.ExecuteNonQuery();
// Response.Write("Data updated successfully");
// con.Close();
//}
protected void GVbind()
{
con.Open();
SqlCommand cmd = new SqlCommand("select * from [dbo].[idus]", con);
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows == true)
{
GridView1.DataSource = dr;
GridView1.DataBind();
}
}
protected void GridView1_RowEditing(object sender, GridViewEditEventArgs e)
{
GridView1.EditIndex = e.NewEditIndex;
GVbind();
}
protected void GridView1_RowUpdating(object sender, GridViewUpdateEventArgs e)
{
int ID = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
string name = ((TextBox)GridView1.Rows[e.RowIndex].Cells[1].Controls[0]).Text;
string phone = ((TextBox)GridView1.Rows[e.RowIndex].Cells[2].Controls[0]).Text;
string address = ((TextBox)GridView1.Rows[e.RowIndex].Cells[3].Controls[0]).Text;
con.Open();
SqlCommand cmd = new SqlCommand("update [dbo].[idus] set name='" + name + "', phone='" + phone + "', address='" + address + "' where ID = '" + ID + "'", con);
int t = cmd.ExecuteNonQuery();
if (t > 0)
{
con.Close();
Response.Write("<script>alert('Data has been updated') </script>");
GridView1.EditIndex = -1;
GVbind();
}
}
protected void GridView1_RowCancelingEdit(object sender, GridViewCancelEditEventArgs e)
{
GridView1.EditIndex = -1;
GVbind();
}
protected void GridView1_RowDeleting(object sender, GridViewDeleteEventArgs e)
{
con.Open();
int id = Convert.ToInt32(GridView1.DataKeys[e.RowIndex].Value.ToString());
SqlCommand cmd = new SqlCommand("delete from [dbo].[idus] where ID='" + id + "'", con);
int t = cmd.ExecuteNonQuery();
if (t > 0)
{
con.Close();
Response.Write("<script>alert('Data has been deleted') </script>");
GridView1.EditIndex = -1;
GVbind();
}
}
protected void DisplayData()
{
SqlConnection con = new SqlConnection("Data Source=MERIH-PC;Initial Catalog=aspidus;Integrated Security=True");
DataTable dt = new DataTable();
SqlDataAdapter da = new SqlDataAdapter("select * from [dbo].[idus]", con);
con.Open();
da.Fill(dt);
con.Close();
GridView1.DataSource = dt;
GridView1.DataBind();
}
protected void GridView1_PageIndexChanging1(object sender, GridViewPageEventArgs e)
{
GridView1.PageIndex = e.NewPageIndex;
GVbind();
'''
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You are assigning the GV a "reader", and you can't use a reader - you have to fill a table, or use some other ennumberable collection. Say like a data table.
So, this code:
protected void GVbind()
{
con.Open();
SqlCommand cmd = new SqlCommand("select * from [dbo].[idus]", con);
SqlDataReader dr = cmd.ExecuteReader();
if (dr.HasRows == true)
{
GridView1.DataSource = dr;
GridView1.DataBind();
}
}
Change to :
protected void GVbind()
{
con.Open();
SqlCommand cmd = new SqlCommand("select * from [dbo].[idus]", con);
Datatable dt = new dt();
dt.load(cmd.ExecuteReader());
GridView1.DataSource = dt;
GridView1.DataBind();
}
So, while you can "shove" the GV to a reader directly? If you going to use paging, then you can't shove into the GV a reader - since paging does not work with a non innumerable type of data set (like a reader).
So, just load up a data table. And note how I did not even need a data adaptor to load up a data table (the data table has a .Load command for you. (so, you can shorten your other code this way also).

Insert and Update Function work on single button click in c#

I am trying to insert and update data using same button. I have created method(uniqueEmail()) to check the email address exist in table or not. Using this method I am trying to insert data if email is not preset.
here is my code please correct me where I am going wrong.
public partial class _Default : System.Web.UI.Page
{
SqlConnection con = new SqlConnection("Data Source=ADMIN-PC\\SQLEXPRESS;Initial Catalog=register;Integrated Security=True");
protected void Page_Load(object sender, EventArgs e)
{
}
public void Button1_Click(object sender, EventArgs e)
{
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
if (uniqueEmail()==true)
{
cmd.CommandText = "update registeruser set email='" + TextBox1.Text + "', password='" + TextBox2.Text + "' where email='" + TextBox1.Text + "'";
}
else
{
cmd.CommandText = "insert into registeruser values('" + TextBox1.Text + "', '" + TextBox2.Text + "')";
}
cmd.ExecuteNonQuery();
con.Close();
}
public bool uniqueEmail()
{
string stremail;
string querye = "select count(email) as email from registeruser";
SqlCommand cmd = new SqlCommand(querye, con);
SqlDataReader dr;
dr = cmd.ExecuteReader();
while (dr.Read())
{
try
{
stremail = dr["email"].ToString();
return(stremail != "0");
if (stremail != "0")
{
//errlblemail.Text = "email already exist";
return false;
}
}
catch (Exception e)
{
string message = "error";
message += e.Message;
}
finally
{
dr.Close();
}
}
return true;
}
}

You need to check for the count of the particular emailId, not the total count.
Modify the code as below:
public static bool uniqueEmail(string email)
{
string stremail;
string querye = "select count(email) as email from register where
email = '" + email + "'";
//Remaining Code
}
public static void Button1_Click(object sender, EventArgs e)
{
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
if (uniqueEmail(TextBox1.Text)) == true)
//Remaining Code
}

#nirmala you should replace method
public void EmailCheck()
{
string constring = ConfigurationManager.ConnectionStrings["ConnData"].ConnectionString;
SqlConnection con = new SqlConnection(constring);
SqlCommand cmd = new SqlCommand("Select * from EmailSignUp where EmailId= #EmailId", con);
cmd.Parameters.AddWithValue("#EmailId", this.txtEmail.Text);
con.Open();
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
if (dr.HasRows == true)
{
MessageBox.Show("EmailId = " + dr[5].ToString() + " Already exist");
txtEmail.Clear();
break;
}
}
}

Two Things need to be done
Pass the Email Id while calling
if (uniqueEmail()==true)
To
if (uniqueEmail(TextBox1.Text)==true)
And in uniqueEmail method chenage the query ()include where condition as below
public bool uniqueEmail(email)
{
string stremail;
string querye = "select count(email) as email from registeruser where email='" + email + "'";
//your remaining code
}

Hi Nirmala your code is correct only you need to put where clause to find the email id already exist in the Database.
public partial class _Default : System.Web.UI.Page
{
SqlConnection con = new SqlConnection("Data Source=ADMIN-PC\\SQLEXPRESS;Initial Catalog=register;Integrated Security=True");
protected void Page_Load(object sender, EventArgs e)
{
}
public void Button1_Click(object sender, EventArgs e)
{
con.Open();
SqlCommand cmd = con.CreateCommand();
cmd.CommandType = CommandType.Text;
if (uniqueEmail()==true)
{
cmd.CommandText = "update registeruser set email='" + TextBox1.Text + "', password='" + TextBox2.Text + "' where email='" + TextBox1.Text + "'";
}
else
{
cmd.CommandText = "insert into registeruser values('" + TextBox1.Text + "', '" + TextBox2.Text + "')";
}
cmd.ExecuteNonQuery();
con.Close();
}
public bool uniqueEmail()
{
string stremail;
string querye = "select count(email) as email from registeruser where email = '" +TextBox1.Text+ "'";
SqlCommand cmd = new SqlCommand(querye, con);
SqlDataReader dr;
dr = cmd.ExecuteReader();
while (dr.Read())
{
try
{
stremail = dr["email"].ToString();
return(stremail != "0");
if (stremail != "0")
{
//errlblemail.Text = "email already exist";
return false;
}
}
catch (Exception e)
{
string message = "error";
message += e.Message;
}
finally
{
dr.Close();
}
}
return true;
}
}

When entering data does not update the text box

Hello friends I am writing to pull information from the base TextBox and I want to update the database through the TextBox , but when I enter the new value is the old value does not always save the new value
Code behind
protected void Page_Load(object sender, EventArgs e)
{
string ID = Request.QueryString["Id"].ToString();
SqlConnection baglan = new SqlConnection(ConnectionString3);
baglan.Open();
SqlCommand com = new SqlCommand("Select * from pkategori where Id='" + ID + "'", baglan);
SqlDataReader oku = com.ExecuteReader();
if (oku.Read())
{
baslik.Text = oku["Tanim"].ToString();
detaylar.Text = oku["Detaylar"].ToString();
}
else
{
baslik.Text = "Bulunmadı";
}
}
Button Click Event
string ust = Request.QueryString["ID"].ToString();
SqlConnection baglanti = new SqlConnection(ConnectionString3);
baglanti.Open();
string kayit = "update pkategori set Tanim=#Tanim where Id=#Id";
SqlCommand komut = new SqlCommand(kayit, baglanti);
komut.Parameters.AddWithValue("#Tanim", baslik.Text);
komut.Parameters.AddWithValue("#Id", ust);
komut.ExecuteNonQuery();
baglanti.Close();

Simple, just wrap your code in Page_Load in a !IsPostBack-check:
protected void Page_Load(object sender, EventArgs e)
{
if(!IsPostBack)
{
string ID = Request.QueryString["Id"].ToString();
SqlConnection baglan = new SqlConnection(ConnectionString3);
baglan.Open();
SqlCommand com = new SqlCommand("Select * from pkategori where Id='" + ID + "'", baglan);
SqlDataReader oku = com.ExecuteReader();
if (oku.Read())
{
baslik.Text = oku["Tanim"].ToString();
detaylar.Text = oku["Detaylar"].ToString();
}
else
{
baslik.Text = "Bulunmadı";
}
}
}
Otherwise you are loading the text from the database and the changed value is overwritten.

Object reference not set to an instance of an object for asp.net

protected void Page_Load(object sender, EventArgs e)
{
lb_msg2.Text = "Hello " + Session["userid"].ToString() + "!";
}
protected void Button1_Click(object sender, EventArgs e)
{
SqlConnection con = new SqlConnection();
con.ConnectionString = ConfigurationManager.ConnectionStrings["ProfileCS"].ConnectionString;
string sql = "Select password from Profile where userid = '" + Session["userid"] + "'";
SqlCommand cmd = new SqlCommand();
SqlDataReader dr; // to hold reference of datareader returned
//prepare a place - datatable to hold the data
DataTable dt = new DataTable();
//setting up command
cmd.CommandText = sql;
cmd.Connection = con;
//connection and execute command
con.Open();
dr = cmd.ExecuteReader();
dt.Load(dr); // copy data from datareader to datatable
string pwdcheck;
pwdcheck = dt.Rows[0]["password"].ToString();
if (tb_verify.Text.Equals(pwdcheck))
{
string password = tb_pwd.Text;
sql = "Update Profile set password ='" + password + "'";
sql = sql + "where userid = '" + Session["userid"] + "'";
cmd.CommandText = sql;
cmd.Connection = con;
try
{
cmd.ExecuteNonQuery();
lb_msg.Text = "Password changed succesfully";
}
catch (Exception ex)
{
lb_msg.Text = "Problems encountered " + ex.Message;
}
finally
{
con.Close();
con.Dispose();
cmd.Dispose();
}
}
else
lb_msg.Text = "Old password Incorrect";
}
protected void lblClick(object sender, EventArgs e)
{
FormsAuthentication.SignOut();
Session.Clear(); // This may not be needed -- but can't hurt
Session.Abandon();
FormsAuthentication.RedirectToLoginPage();
}
}
lb_msg2.Text = "Hello " + Session["userid"].ToString() + "!";
there is an error at the line above with
Object reference not set to an instance of an object the change password feature was working before.

In your case Session["userid"] must be NULL,handle it

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();
}