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can someone tell me ???. Why the following code is not working ???. let me know some idea.Code:private bool OpenConnection(ref OleDbConnection conn)
{
try
{
conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Imp\product_Table.mdb");
conn.Open();
if (conn.State!=conn.Open )
{
MessageBox.Show("Connection is Not Open");
return false;
}
else
{
return true;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return false;
}
}
vb Code:
Should be:
vb Code:
That should be
Code:if (con.State != ConnectionState.Open)
{
}
Still not working .it says The name 'ConnectionState' does not exist in the current context.here is the following code.
Code:private bool OpenConnection(ref OleDbConnection conn)
{
conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Imp\product_Table.mdb");
conn.Open();
if (conn.State!=ConnectionState.Open )
{
MessageBox.Show("Connection is Not Open");
return false;
}
else
{
return true;
}
}
}
}
You are missing namespace System.Data
Code:if (con.State != System.Data.ConnectionState.Open )
Resolved
Not working means ?Quote:
Originally Posted by firoz.raj
here is a better and more elegant code:
shorter lines of code and easy to read.Code:private bool OpenConnection(ref OleDbConnection conn)
{
conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Imp\product_Table.mdb");
conn.Open();
return conn.State == ConnectionState.Open;
}
why the following code is not working ???.i simple want to fill my dataset.after filliling the listbox.let me know some idea.Quote:
here is a better and more elegant code:
Code:private void BtFillListBox_Click(object sender, EventArgs e)
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "Select * from employees";
DataSet ds = new DataSet("Employees");
OleDbDataAdapter MyAdapter = new OleDbDataAdapter();
// MyAdapter.SelectCommand = OleDbCommand;
MyAdapter.Fill(ds, "Employees");
}
when you say it doesnt work, what happens?
you commented out the MyAdapter.SelectCommand. this is incorrect, the DataAdapter needs this to execute the select command to fill the dataset. this select command is stored in the object you created called cmd.
MyAdapter.SelectCommand = cmd;
Still i am getting error .Select Command.Connection Property has not been initialized.here is the following code.what i have written.let me know please .Code:using System;
using System.Data.OleDb ;
using System.Windows.Forms;
using System.Data;
namespace MakeConnection
{
public partial class Form1 : Form
{
private OleDbConnection conn = new OleDbConnection();
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
filllistbox();
}
public bool OpenConnection()
{
try
{
// OleDbConnection conn = new OleDbConnection();
conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=C:\Imp\product_table.mdb");
conn.Open();
if (conn.State!=ConnectionState.Open )
{
MessageBox.Show("Connection is Not Open");
return false;
}
else
{
return conn.State == ConnectionState.Open;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
return false;
}
}
private void CloseConnection()
{
try
{
if (conn.State == ConnectionState.Open )
{
conn.Close() ;
}
conn.Dispose();
}
catch(Exception ex)
{
MessageBox.Show(ex.Message);
conn.Close();
}
}
private void filllistbox()
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "Select * from employees";
OleDbDataAdapter dataloader = new OleDbDataAdapter();
dataloader.SelectCommand = cmd;
DataSet ds = new DataSet("Employees");
dataloader.Fill(ds, "Employees");
}
}
}
you should read the MSDN Documentation on how to use the DataAdapter classes.
you need to assign, as it says, the connection property of the select command.
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "Select * from employees";
cmd.Connection = this.conn;
still i am getting error .when i tried to run.additional what is the uses of this.conn.here is it this Pointer ???.when i run using f8. i got the the following error.Quote:
you should read the MSDN Documentation on how to use the DataAdapter classes.
you need to assign, as it says, the connection property of the select command.
The SelectCommand property has not been initialized before calling 'Fill'.
Code:private void filllistbox()
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "Select * from employees";
cmd.Connection =this.conn ;
OleDbDataAdapter dataloader = new OleDbDataAdapter();
// dataloader.SelectCommand = cmd;
DataSet ds = new DataSet("Employees");
dataloader.Fill(ds, "Employees");
}
I had stated the error previously and corrected the code :)
how should i fill listbox ???.let me know please.any help would be highly appreciated.Code:private void filllistbox()
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
OleDbCommand cmd = new OleDbCommand();
cmd.CommandText = "Select * from employees";
cmd.Connection =this.conn ;
OleDbDataAdapter dataloader = new OleDbDataAdapter();
// dataloader.SelectCommand = cmd;
DataSet ds = new DataSet("Employees");
dataloader.Fill(ds, "Employees");
ListBox lbox = new ListBox();
}
not sure why you are creating a listbox control in code unless you are going to be adding it to the form dynamically?
simply set the datasource, datamember properties on the listbox in question to the dataset/datatable
still i am getting error at this line For Each row As DataRow In ds.Tables(0).Rows.let me know someone please.here is the following code.what i have written.Quote:
simply set the datasource, datamember properties on the listbox in question to the dataset/datatable
Code:private void filllistbox()
{
if (!OpenConnection())
{
MessageBox.Show("Connection is Not Open");
this.Dispose(true);
}
OleDbCommand cmd = new OleDbCommand();
cmd.CommandType = CommandType.Text;
cmd.CommandText = "Select * from employees";
cmd.Connection =this.conn ;
OleDbDataAdapter dataloader = new OleDbDataAdapter();
dataloader.SelectCommand = cmd;
DataSet ds = new DataSet("Employees");
dataloader.Fill(ds, "Employees");
For Each row As DataRow In ds.Tables(0).Rows
{
ListBox1.Items.Add(row("Name").ToString);
}
}
Don't just tell us that there's an error. If there's an error then there's an error message. The IDE gives it to you to help you solve the problem. Logic dictates that, if you want us to help you solve the problem, you give it to us. You've already been prompted to do that at least twice in this thread alone.
the code you have highlighted you are using is VB.NET. but you are using C#. these are 2 different languages. you need to convert your code to C# equivelent.
foreach(DataRow currentRow in ds.Tables[0].Rows)
{
...
}
still i am getting one error .'System.Data.DataRow' is a 'type' but is used like a 'variable'.datarow is a type means let me clarify please.
try to read the error message and understand what it means. your syntax is also incorrect. Are you using Visual Studio IDE? if so, then there is no excuse or any reason why your syntax should be incorrect
listBox1.Items.Add(DataRow("Name").tostring);
should be
listBox1.Items.Add(currentRow["Name"].tostring);
incorrect
take a look at your syntax.
how many visual IDE Is Available?.additional when i tried to run the following code .i am still getting error. 'currentRow' is a 'variable' but is used like a 'method'Quote:
Are you using Visual Studio IDE? if so, then there is no excuse or any reason why your syntax should be incorrect
First up, in post #22 you were told that you need to change DataRow("Name") to currentRow["Name"] and you've instead changed it to currentRow("Name"). If you aren't going to follow the advice that people provide then there's not much point asking for it.
You've also been told MANY times that C# is a case-sensitive language and you still choose to ignore that. There is no method named "tostring". There is, however, a method named "ToString". Finally, while VB allows you to omit the parentheses on methods if the argument list is empty, C# requires ALL method calls to include parentheses.
i was hoping he'd be able to guess the tostring bit himself lolQuote:
Originally Posted by Techno
yes now the code is working fine.additional can you tell me what is the uses of this keyword here??? .is it this pointer like c++??.let me clarify please.
Code:cmd.Connection =this.conn ;
VB -> Me == C# ->this
:D
.as we know executeNonQuery Function returns No of Rows Affected.in the following code i want to see.how much record has beed deleted.but i am getting error.cannot convert from 'method group ' to 'string'.let me know please.Code:private void Del()
{
Int64 d;
OleDbCommand cmd=new OleDbCommand();
cmd.Connection =this.conn;
cmd.CommandText ="DELETE CDs.ArtistName FROM CDs";
:)
MessageBox.Show(d.ToString );
}
private void Delete_Click(object sender, EventArgs e)
{
Del();
}
As I have already stated, C# requires you to include parentheses on every method call, whether you're passing parameters or not. ToString is a method. You can't call it without parentheses.
It doesn't matter anyways, since the command doesn't get executed... the code as it stands will simply display "0" in the messagebox.
-tg
it is working nice .what is a issue in the above code ???.Additional i have tried to insert textbox data into the listbox.but getting error at red line.let me know please.[Code]private void BtAdd_Click(object sender, EventArgs e)Quote:
It doesn't matter anyways, since the command doesn't get executed... the code as it stands will simply display "0" in the messagebox.
CommandText requires a string.
you arent providing a string.
Still i am getting expected error ;.at the following line.Kindly let me know the idea
Quote:
Originally Posted by firoz.raj
Code:cmd.CommandText ="insert into CDs(ArtistName) Values ('"txtArtistName.Text"')";
still i am getting ; Expected Error.at the following line .
Code:cmd.CommandText ="insert into CDs(ArtistName )values ('"txtArtistName.text"')";
because you need to add the value of txtArtistName.Text into the string.
cmd.CommandText ="insert into CDs(ArtistName )values ('" + txtArtistName.text + "')";
for best practice you should be using StringBuilder to concatinate string as well as using SPROCS (Stored Procedures) for data insertion, deletion and retrieval for security and performance
Well.Can SomeOne Tell me ?How should i refresh the list Box.after adding data
it should immediately go in the listbox.let me know please.:wave:Code:private void BtAdd_Click(object sender, EventArgs e)
{
OleDbCommand cmd = new OleDbCommand();
cmd.Connection = this._conn;
cmd.CommandText ="insert into CDs(ArtistName )values ('" + txtArtistName.Text + "')";
cmd.ExecuteNonQuery();
//filllistbox();
}
you need to rebind the data. so you need a method which binds the data and call that method.
can you post the code you currently have? it would help
Can You tell me ?How should I write DataBase Path in the settings area af the properties ?let me know please.When tried to Click on settings nothing happens.so let me know How should I assign path there???.
Thx in Advance.
well typically a connectionstring looks like this:
Data Source=computerName\SQLSERVERINSTANCE;Initial Catalog=Databasename;Trusted_Connection=true;
replace data source and initial catalog values appropriately.
if you are NOT using SQL Server Express, then the data source is typically just a local pointer example:
local
(local)
.
if you are using SQL Server Express, then the instance name is SQLExpress:
.\SQLExpress
but i am using DataBase Ms Access 2007.let me know please!!!:D:D:DQuote:
well typically a connectionstring looks like this:
Data Source=computerName\SQLSERVERINSTANCE;Initial Catalog=Databasename;Trusted_Connection=true;
replace data source and initial catalog values appropriately.
if you are NOT using SQL Server Express, then the data source is typically just a local pointer example:
local
(local)
.
if you are using SQL Server Express, then the instance name is SQLExpress:
.\SQLExpress
sure. in which case the connectionstring differs.
you need to import the System.Data and System.Data.OleDB namespace to gain access to the OleDBConnection and OleDBCommand classes which will do what you pretty much want and operate similarly to the Sql classes.
www.connectionstrings.com contains all the possible connection strings.
http://msdn.microsoft.com/en-us/libr...(v=VS.80).aspx
I Simple want if specific Text exists in the fields( Identity) in the specific table(IdentityTab). Method needs to return true . otherwise false .i did flow . but I don’t know how should I Achieve the following Method ??? Using C# Code. which I did in Vsd . Using OleDbCommand object and the OleDbDataReader in c#
:(Code:public bool Identification(string identifier) {
using (OleDbConnection conn=new OleDbConnection(_path)){
conn.Open();
using (OleDbCommand Cmd = new OleDbCommand(_path)){
Cmd.CommandText = "Select identityNo from identityTab";
how should i check specific text in a fields of Specific Table ???.
if found
return true ;
}
return false;
}
well you are almost there. in this case, you should use oleDbDataReader which is a fast forward only reader. so executeReader on your OleDbCommand, which returns you an OleDbDataReader, then see if there is a record returned by calling it's Read() method, which returns a bool.
an example and documentation of the class:
http://msdn.microsoft.com/en-us/libr...er(VS.71).aspx
I need using vsd logic . let me know . how should I Achieve it ???.How should I check Specific text in the field of the table .:(
looks like homework to me. a link was given which explains how the class works, with an example. you need to read the documentation and understand it to implement your VSD logic.
hint: the reader has an index you can specify to read a field value.
[Quote]looks like homework to me. a link was given which explains how the class works, with an example. you need to read the documentation and understand it to implement your VSD logic.
hint: the reader has an index you can specify to read a field value.
[FONT="Comic Sans MS" How should I check specific Index Using Reader Property ??????????? .[/FONT]:(
by specifying the indexing characters. or you can use GetString method to get a string value of the specified column index.
example:
reader[ColumnIndexHere]
this will read the value of the specified column index
however your code is still wrong. OleDbDataReader is not an instantiable class.
Still the same.
Calm down. You're talking like freaking Yoda, and panicking at the same time and it's not helping the situation.
Think for a moment about the code you posted and why it doesn't work (by the way, that's two trout slaps for not mentioning the error message.)
You pass in a parameter "identifier" ... but then never use it any where. Then you use a variable called "identityNo" which is never defined anywhere. AND you use it as the indexor of the reader array. Then you're comparing what I'm assuming to be a numerical field to the boolean value of true.
-tg
Quote:
you use a variable called "identityNo" which is never defined anywhere. AND you use it as the indexor of the reader array. Then you're comparing what I'm assuming to be a numerical field to the boolean value of true.
I Have tried but still I am getting the same error !!!.
:(Code:public bool Identification(string identifier){
using (OleDbConnection conn = new OleDbConnection(_path)){
conn.Open();
using (OleDbCommand Cmd = new OleDbCommand(_path)){
Cmd.CommandText = "Select identityNo from identityTab where identityTab.IdentityNo="+identifier ;
return true;
}
return false;
}
}
1) Stop yelling... that's not going to accomplish anything other than offending those who are doing their best to help.
2) what is _path? I'm guessing that it is your connection string, right? Then you pass it to your connection (which you are - good) but you do NOT pass it to your command object.
3) The only things you should be passing to your command object is your connection and your sql statement. at a minimum, you should be passing the connection (but not the _path).
4) You've created the command object set the command text, but never execute it.
5) You may want to consider reading through our Database FAQs and Tutorials there's some good stuff in there, including the basics of how to talk to your database. And how to use parameters too.
-tg
At first Identifier is a text .when I write single quote .i am getting error Newline is Constant !!!.
Cmd.CommandText = "Select identityNo from identityTab where identityTab.IdentityNo="' +identifier+ ' " ;:(
I see one issue that is very obvious.Quote:
Originally Posted by firoz.raj
This should solve the very obvious issue. Always double check when combining strings if you require an ' remember to have it inside the ". As you can see in your example, neither are within the realm of the quotations and therefore you should be receiving an error.Code:Cmd.CommandText = String.Concat( "Select identityNo from identityTab where identityTab.IdentityNo='", identifier, "'");
To be perfectly honest, even the ' isn't necessary. If it's a number, treat it like a number, not a string.
-tgCode:Cmd.CommandText = String.Concat( "Select identityNo from identityTab where identityTab.IdentityNo=", identifier);