How do I loop through rows with a data reader in C#?

I know I can use while(dr.Read()){...} but that loops every field on my table, I want to retrieve all the values from the first row, and then second... and so on.

Let's say I have a table like this:

ID--------------Value1--------------Value2------------------Value3
1               hello               hello2                  hello3
2               hi1                  hi2                      hi3

first I want to get, hello, hello2 and hello3 and then go to the second row and get all the values.

Is there a way to achieve this? I hope somebody understand what I mean.

I am so sorry, this is solved now. I just wasn't coding right...

And yeah the SqlDataReader.Read() method does what it is supposed to do, again the mistake was mine.

That's the way the DataReader works, it's designed to read the database rows one at a time.

while(reader.Read()) 
{
  var value1 = reader.GetValue(0); // On first iteration will be hello
  var value2 = reader.GetValue(1); // On first iteration will be hello2
  var value3 = reader.GetValue(2); // On first iteration will be hello3
}

int count = reader.FieldCount;
while(reader.Read()) {
    for(int i = 0 ; i < count ; i++) {
        Console.WriteLine(reader.GetValue(i));
    }
}

Note; if you have multiple grids, then:

do {
    int count = reader.FieldCount;
    while(reader.Read()) {
        for(int i = 0 ; i < count ; i++) {
            Console.WriteLine(reader.GetValue(i));
        }
    }
} while (reader.NextResult())

Or you can try to access the columns directly by name:

while(dr.Read())
{
    string col1 = (string)dr["Value1"];
    string col2 = (string)dr["Value2"];
    string col3 = (string)dr["Value3"];
}

There is no way to get "the whole row" at once - you need to loop through the rows, and for each row, you need to read each column separately:

using(SqlDataReader rdr = cmd.ExecuteReader())
{
    while (rdr.Read())
    {
        string value1 = rdr.GetString(0);
        string value2 = rdr.GetString(1);
        string value3 = rdr.GetString(2);
    }
}

What you do with those strings that you read for each row is entirely up to you - you could store them into a class that you've defined, or whatever....

> How do I loop through rows with a data reader in C#?

IDataReader.Read() advances the reader to the next row in the resultset.

while(reader.Read()){
    /* do whatever you'd like to do for each row. */
}

So, for each iteration of your loop, you'd do another loop, 0 to reader.FieldCount, and call reader.GetValue(i) for each field.

The bigger question is what kind of structure do you want to use to hold that data?

Actually the Read method iterating over records in a result set. In your case - over table rows. So you still can use it.

while (dr.Read())
{
    for (int i = 0; i < dr.FieldCount; i++)
    {
        subjob.Items.Add(dr[i]);
    }
}

to read rows in one colunmn

Suppose your DataTable has the following columns try this code:

DataTable dt =new DataTable();
txtTGrossWt.Text = dt.Compute("sum(fldGrossWeight)", "").ToString() == "" ? "0" : dt.Compute("sum(fldGrossWeight)", "").ToString();
txtTOtherWt.Text = dt.Compute("sum(fldOtherWeight)", "").ToString() == "" ? "0" : dt.Compute("sum(fldOtherWeight)", "").ToString();
txtTNetWt.Text = dt.Compute("sum(fldNetWeight)", "").ToString() == "" ? "0" : dt.Compute("sum(fldNetWeight)", "").ToString();
txtFinalValue.Text = dt.Compute("sum(fldValue)", "").ToString() == "" ? "0" : dt.Compute("sum(fldValue)", "").ToString();