need immediate help

[rajasavi]

hi,
i m rajasavi.have just studied learning VB.net and need some help .i m making small window application using database about getting verfiying password before entering the other page.but my problem how to apply the constraint that only 1 user should have same name..should i use the constarint in database or should is there anyway of checking this in aplication code.

also help me out of hw to use ILDASM as it gives error P.E cannot be created

[radcaesar]

hi,
i m rajasavi.have just studied learning VB.net and need some help .i m making small window application using database about getting verfiying password before entering the other page.but my problem how to apply the constraint that only 1 user should have same name..should i use the constarint in database or should is there anyway of checking this in aplication code.

also help me out of hw to use ILDASM as it gives error P.E cannot be created

Make ur UserName Column as a Unique Column in DB and catch the exception in the c# code when the user tries to insert a duplicate user name

[Habeebuddin]

Hi,
You can impose that constraint of ensuring unique users in the application code itself. Check whether the name entered in the textbox(username) is already exists in the table(in database) by parsing through the records...

for ex:
.....
.....
dataAdapter.Fill(dataSet);
int userFound=0;
int i=0;
for(i=0;i<dataSet.Tables[0].Rows.Count;i++)
{
if(dataSet.Tables[0].Rows[i][0].ToString()==txtUser.Text)
userFound=1;
if(userFound==1)
break;
}
if(userFound==1)
// error
else
// User exists

Hope this is useful....

[anaphaxeon]

Oh god that looked complex, make your select statement like this.
//
public bool UserExists
{
get
{
string select = "SELECT Username FROM Users WHERE Username = '" + UsernameVariable + "'";

//I'll assume you already have a SqlDataConnection called sqlConn

DataAdapter da = new DataAdapter(select,sqlConn)
DataTable dt = new DataTable();
da.Fill(dt);
return dt.Rows.Count >0
}
}

[anaphaxeon]

Now with that code you could easily verify that the user exists without iterating through all the rows (which costs performance), plus returning a massive amount of rows from SQL costs performance, and memory.

Now to use this, it's real easy. Before saving just do this.

if(UserExists)
{
MessageBox.Show("This username is already in use!","Error",MessageBoxButtons.Ok,MessageBoxIcon. Error);
}
else
{
SaveUserMethod();
}

[anaphaxeon]

Please give more feedback on ILDASM, in order to use the disassembly module the component has to be a .NET component, otherwise you would have to use tlbimp.exe to translate the component to .NET.