Re: how to take a table name from a text box! - C# Discussion Boards

Re: how to take a table name from a text box!

Luc Pattyn3-Jan-12 8:04

3-Jan-12 8:04

IMO the answer holds two parts:

1. don't use a TextBox, use a ComboBox (with ComboBoxStyle.DropDownList) presenting the allowable table names.
2. then perform string concatenation to build the SQL statement.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: how to take a table name from a text box!

AHSAN1114-Jan-12 4:38

AHSAN111

4-Jan-12 4:38

the dropdown list would eliminate the facility of having tablenames according to user choices. This IMO is essential if we are dealing with a SQL Parser or a simillar application, or a situation where we need user-specified entity names in the database.

We can use a textbox and employ reguler expressions / validation controls in order to eliminate the possibility of an incorrect tablename.

Re: how to take a table name from a text box!

Luc Pattyn4-Jan-12 4:49

Luc Pattyn

4-Jan-12 4:49

Something needs to be done to protect against abuse. Validation is one way, yes.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: how to take a table name from a text box!

AHSAN1113-Jan-12 22:02

AHSAN111

3-Jan-12 22:02

Try the following:

string q = "create table " + Textbox1.text + "(enum number,ename varchar2(10),sal number)";

a better way (cleaner and easily readable) of doing it would be to use a local string variable to store the table name from the text box and concatenate the string using that variable.

string temp = Textbox1.Text;
string q = "create table "+temp+ " (enum number,ename varchar2(10),sal number)";

Re: how to take a table name from a text box!

Luc Pattyn4-Jan-12 3:14

Luc Pattyn

4-Jan-12 3:14

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: how to take a table name from a text box!

AHSAN1114-Jan-12 4:31

AHSAN111

4-Jan-12 4:31

why did u downvote ?? please explain Smile | :)

Re: how to take a table name from a text box!

Luc Pattyn4-Jan-12 4:41

Luc Pattyn

4-Jan-12 4:41

I disliked very much however I did not downvote.
Your code would not compile.
And it is flawed, see my other posts in this thread.

Hmmm | :|

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: how to take a table name from a text box!

mpvkrishnadhar4-Jan-12 4:23

mpvkrishnadhar

4-Jan-12 4:23

hi
AHSAN111!

thanks for the reply mate! the first and the second parts that u explained are working fine for me!

this is how my new code looks like!

try
{
string constr = "User Id = scott;Password=tiger;Provider=Msdaora.1";
OleDbConnection con = new OleDbConnection(constr);
con.Open();
MessageBox.Show(" Connected to ORACLE!");
string g = textBox1.Text;
string q = "create table " +g+ "(enum number,ename varchar2(10),sal number)";
OleDbCommand cmd = new OleDbCommand(q, con);
cmd.ExecuteNonQuery();
MessageBox.Show("Table Created!");
}

Re: how to take a table name from a text box!

Luc Pattyn4-Jan-12 4:34

Luc Pattyn

4-Jan-12 4:34

that is bad code, it is open for SQL injection, people can type anything they like in the TextBox and make your program execute it.

I already told you precautions had to be taken against it, using a uneditable ComboBox rather than a TextBox is one way of doing just that.

Smile | :)

Luc Pattyn [My Articles] Nil Volentibus Arduum

Re: how to take a table name from a text box!

mpvkrishnadhar4-Jan-12 4:53

mpvkrishnadhar

4-Jan-12 4:53

ooh!

but if i use comboboxstyle with allowable table names! the whole purpose of what i wanted would not be served! is there any way by which it can be done! ? but thank u very much for the suggestion mate! am seriously learning a lot from this!

Re: how to take a table name from a text box!

AHSAN1115-Jan-12 2:18

AHSAN111

5-Jan-12 2:18

As I said, you need to use a validator to ensure that only allowable table names are used to construct the query. You can use javascript + regex or .net validation controls as it suites you.

when i delete my program (in C#) the database still exists - how to delete him ?

goldsoft3-Jan-12 4:51

goldsoft

3-Jan-12 4:51

hi when i delete my program (in C#) through add/remove programs
the database still exists - how to delete him ?
thanks in advance

Re: when i delete my program (in C#) the database still exists - how to delete him ?

Richard Andrew x643-Jan-12 6:00

Richard Andrew x64

3-Jan-12 6:00

You can create a custom action in your installer that runs when the product is uninstalled.

The custom action would call a function in one of your DLL's that removes any files created by the program after it was installed.

The difficult we do right away...
...the impossible takes slightly longer.

Re: when i delete my program (in C#) the database still exists - how to delete him ?

Gali19783-Jan-12 9:33

Gali1978

3-Jan-12 9:33

thanks for the help !
how to make custom action to my installer ?

Re: when i delete my program (in C#) the database still exists - how to delete him ?

Richard Andrew x643-Jan-12 9:36

Richard Andrew x64

3-Jan-12 9:36

What are you using to create the install package?

The difficult we do right away...
...the impossible takes slightly longer.

Re: when i delete my program (in C#) the database still exists - how to delete him ?

PIEBALDconsult3-Jan-12 7:39

PIEBALDconsult

3-Jan-12 7:39

"All your database is belong to us." -- Microsoft

Re: when i delete my program (in C#) the database still exists - how to delete him ?

Paladin20003-Jan-12 9:49

Paladin2000

3-Jan-12 9:49

What you say?!

OdbcDataReader calling IsDBNull changes the behaviour of Get methods

__John_3-Jan-12 3:16

__John_

3-Jan-12 3:16

Hi,

If I do...

int nColName   = odbcDataReader.GetOrdinal(@"name");
int nColNumber = odbcDataReader.GetOrdinal(@"iq");

while (odbcDataReader.Read())
{
    string strName = odbcDataReader.GetString(nColNumber);
    int nNumber = odbcDataReader.GetInt32(nColNumber);
}

GetString() succeeds.
GetInt32() throws an exception... [System.InvalidCastException] = {"Specified cast is not valid."}

However if I do...

int nColName   = odbcDataReader.GetOrdinal(@"name");
int nColNumber = odbcDataReader.GetOrdinal(@"iq");

while (odbcDataReader.Read())
{
    odbcDataReader.IsDBNull(nColNumber);

    int nNumber = odbcDataReader.GetInt32(nColNumber);

    string strNumber = odbcDataReader.GetString(nColNumber);

}

Now GetInt32() succeeds.
And GetString() throws an exception... [System.InvalidCastException] = {"Unable to cast object of type 'System.Int32' to type 'System.String'."}

FYI: The column in question 'IQ' is of type 'int'.

It seems that calling IsDBNull() first, changes the behaviour of the Get methods.

Can anyone explain what is going on?

Thanks - John.

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

kevinnicol3-Jan-12 3:46

kevinnicol

3-Jan-12 3:46

My only guess at this point is in the first test you are calling GetString first, and in the second test you are calling GetInt32 first. It's possible the the reader is casting your value to what you asked for first?

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

__John_3-Jan-12 4:10

__John_

3-Jan-12 4:10

Hi kevinnicol,

The only reason for putting them in a different order is because I put the call that throws the exception last.

Changing the order just means that you never get to second call because the first throws an exception.

@PIEBALDconsult: Yes, I should check the return but it makes no differance to my question.

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

Dan Mos3-Jan-12 4:18

Dan Mos

3-Jan-12 4:18

Shouldn't it be like:

while (odbcDataReader.Read())
    {
        string strName = odbcDataReader.GetString(nColNumbernColName);
        int nNumber = odbcDataReader.GetInt32(nColNumber);
    }

__John_ wrote:
@PIEBALDconsult: Yes, I should check the return but it makes no differance to my
question.

I beg to differ. If it's true e.g. the value is null it will throw an exception on the int part.
Ints can't be null. Either use a nullable int? or check for null first.

All the best,

Dan

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

__John_3-Jan-12 4:24

__John_

3-Jan-12 4:24

Non of the returns are null so checking makes no fifferance.

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

Dan Mos3-Jan-12 4:26

Dan Mos

3-Jan-12 4:26

Then yes. But you failed to specify that.

Honestly I'm out of ideas. Maybe a stupid question like "what is the DB type?" is all I got left.

Maybe it should be long or short or... on the C# side.
Smile | :)

All the best,

Dan

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

__John_3-Jan-12 4:35

__John_

3-Jan-12 4:35

Hi MDL=>Moshu, thanks for the reply.

The cast that fails is internal to the Get methods. So for example...

var Val = odbcDataReader.GetInt32(nColNumber);

Still thows the same exception.

I am using the data provider for MS SQL Sever that came with vs2010.

SQL Server version is 2008.

Thanks - John.

Re: OdbcDataReader calling IsDBNull changes the behaviour of Get methods

Dan Mos3-Jan-12 4:41

Dan Mos

3-Jan-12 4:41

In your statement var Val is the same as int Val cause GetInt32() returns a int on success.

var Val = odbcDataReader[nColNumber]; is what you should use.
Val will be an object of type Object and you can check for null and do the casting later.

This is obviously for debugging purposes. Cause the cast and checking are not necessarily once you figure
out the problem.

All the best,

Dan

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