How to work with multiple result sets using SqlDataReader?

Introduction

ADO.NET is a mechanism to communicate with the database. It allows us to work in connected (database connection is alive while the operation is performed) as well as disconnected architecture (database connection is closed and operation can be performed on the data).

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In order to retrieve more than one result sets using Stored Procedure or multiple select statements in one go using SqlDataReader, we can follow this approach.

Below is the GridView code on my ASPX Page

ASPX PAGE

<asp:GridView ID="GridView1" runat="server" EnableViewState="false" />
 <hr />
 <asp:GridView ID="GridView2" runat="server" EnableViewState="false" />

In above code snippet, we have two GridViews in which we shall bind both result sets.

CODE BEHIND

   string _connStr = ConfigurationManager.ConnectionStrings["ConnStr"].ConnectionString;
 
  protected void Page_Load(object sender, EventArgs e)
  {
     // get the connection
     using (SqlConnection conn = new SqlConnection(_connStr))
     {
         // write the sql statement to execute
         string sql = "SELECT AutoID, FirstName, LastName, Active FROM
PersonalDetail ORDER BY FirstName; " +
            "SELECT AutoId, FileName FROM Files Order By FileName ASC";
            // instantiate the command object to fire
            using (SqlCommand cmd = new SqlCommand(sql, conn))
            {
               conn.Open();
               // in case of multiple result set you will not be able to specify the
CommandBehavior
               // if so you will not be able to get the next result set from the
reader
 
              using (SqlDataReader reader = cmd.ExecuteReader())
              {
                 // bind the first resultset
                 GridView1.DataSource = reader;
                 GridView1.DataBind();
 
                 reader.NextResult();
 
                // bind the second resultset
                GridView2.DataSource = reader;
                GridView2.DataBind();
            }
            conn.Close();
        }
    }
}

In the code behind, we have executed two SQL statements (sql string variable has two SELECT statements separated by ";") in the SqlDataReader.

The first result set can be accessed by simply calling the reader object however to access the second result set, we need to explicitly call the NextResult method of the reader object.

Notice that we will not be able to specify the CommandBehavior.CloseConnection while executing the reader from the command object in this case (when the reader is returning two result sets), if so it throws following error while trying to access the next result set.

Exception Details: System.InvalidOperationException: Invalid attempt to call NextResult when reader is closed.

OUTPUT

Hope this article was useful, do let me know your comment or feedback.

In case you are looking for returning multiple results set using DataSet, use this article.

Stay tuned for many more articles and do not forget to refer these articles to your friend in need.

Thanks for reading.