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

Question

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 o

Answer 1

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....

Answer 2

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"];
}

Answer 3

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();

Answer 4

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

Answer 5

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

to read rows in one colunmn

Answer 6

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?