ASP.NET question (easy)

[Martin]

so I'm just learning asp.net, but I can't seem to access the data stored in a database.

I have a database with a tables named "Users" with three columns: id, alias, password.

Now, I made and filled a DataSet and mapped the users Table to it, but I can't access the data in individual cells.

here is the code I am having trouble with


foreach (DataRow myRow in dsUsers.Tables["users"].Rows) {
msg = myRow["alias"];
}

alias.Text = msg.ToString();


The problem is, this returns an object, and I want the actual value inside the cell (string in this case)

 

[DAGTA]

I wrote almost entirely in C# so my VB syntax isn't as strong. Look for a .Text or a .Value member inside of that object. I think that will get you what you want.
-DAGTA

 

[GtPrOjEcTX]

haven't used .net but the old asp way was to use the .value to get it...maybe that still works.

 

[Martin]

this is C# and according to MSDN you access an DataRow's value, you use its .Item property. In C#, this is supposed to by done by a method similar to arrays saying objectname[index], for example currentRow[0].

for some reason it doesn't work in my app.

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpref/html/frlrfSystemDataDataRowClassTopic.asp

 

[Martin]

on closer look (I dunno why I didn't see this before), it seems it IS supposed to return the data as an Object.
http://msdn.microsoft.com/library/en-us/cpref/html/frlrfsystemdatadatarowclassitemtopic1.asp


so I guess the question becomes, how do I get the value/data from the Object?

 

[oog]

I don't quite get what you're asking.

myRow["alias"] should get the value of the "alias" column in your DataTable, which is of type Object. When you call myRow["alias"].ToString(), it should get you the value as a string. (In other words, I don't see what's wrong with what you've written)

What are you seeing in alias.Text instead?

 

[oog]

I tried your code in a quick web page I threw together. I preceded your code with some additional code to create the DataSet. Here is what I have below:

DataSet dsUsers = new DataSet();
DataTable userTable = dsUsers.Tables.Add("users");
userTable.Columns.Add("id", typeof(int));
userTable.Columns.Add("alias", typeof(string));
userTable.Columns.Add("password", typeof(string));

userTable.Rows.Add(new object[] { 1, "user1", "pwd1" });
userTable.Rows.Add(new object[] { 1, "user2", "pwd2" });

object msg = null;
foreach (DataRow myRow in dsUsers.Tables["users"].Rows)
{
msg = myRow["alias"];
}

alias.Text = msg.ToString();

The code works fine. The foreach loop runs until we reach the second row, and the text assigned to alias.Text is set to "user2". Is this what you're getting?

 

[Martin]

oog, your code does work, so it seems there must be something wrong with my database connection (perhaps I have no mapped the tables correctly or something)

Thanks for your help.

 

[Martin]

I guess I haven't initialized the dataset tables properly, because when I use my dataset instead of constructing one like you did, I get an error saying object points to null reference.

I will work on the page later and post an update.

 

[oog]

Can you show how you are getting data into the DataSet? You can hide your connection string if that contains some kind of user id and password.

 

[Martin]

Originally posted by: oog
Can you show how you are getting data into the DataSet? You can hide your connection string if that contains some kind of user id and password.

Oh no, I just thought it was irrelevant, that's why I didn't post it. But I found out my problem yesterday, and now it works alright.

The problem was that I was calling

daUsers.Fill(dsUsers); (dataadapter filling in a dataset)

when I changed it to

daUsers.Fill(dsUsers, "users");

everything worked out fine. I guess the first method didn't properly transfer the tables from the database into the dataset.

 

[oog]

Yeah, without that second parameter, I think it doesn't assign a name to the table in the DataSet. You can still access it as dsUsers.Tables[0], but not as the table "users".

 

[Descartes]

Originally posted by: oog
Yeah, without that second parameter, I think it doesn't assign a name to the table in the DataSet. You can still access it as dsUsers.Tables[0], but not as the table "users".

I'm late to this thread, but you are correct. It by default assigns the names incrementally: Table1, Table2, ...

You can also generate a typed dataset to access the tables/fields in a typesafe manner.

 

[Martin]

thanks for all your help.