Question

I have been learning from a tutorial on Home and Learn about setting up databases. Currently, I’m learning about finding records in a database. I’m trying to get my GO! button search for a ingredient in my data table, and I”ve followed the tutorial thoroughly and have no errors in my Error list, but this line of code:

returnRows = dataRecipe.Tables["CookBookRecipes"].Select("Ingredients = '" + searchOut + "'");

It stops my program, and brings up this message:

Object reference not set to an
instance of an object.

I’ve searched the meaning, and I guess it means my returnRows variable is null, but I can’t be sure. Can someone help me fix this problem?

Here is my full code in my Search button:

System.Data.SqlClient.SqlConnection con;
System.Data.SqlClient.SqlDataAdapter dataAdapt;
DataSet dataRecipe;

private void btnSearch_Click(object sender, EventArgs e)
{

    if (tbSearch.TextLength >= 1)
   {
        MessageBox.Show("This will work when you put it a word!");

        // Search code //

        string searchOut = tbSearch.Text;
        int result = 0;
        DataRow[] returnRows;

        returnRows = dataRecipe.Tables["CookBookRecipes"].Select("Ingredients = '" + searchOut + "'");


        result = returnRows.Length;

        if (result > 0)
        {
            DataRow rowBack;
            rowBack = returnRows[0];
            MessageBox.Show(rowBack[3].ToString());
        }
        else
        {
            MessageBox.Show("No such record");
        }

   }

   else
    {
       MessageBox.Show("Please enter an ingredient to search for!", "Search");
   }
}

Here is the full code of my form:

using System; 
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace Cookbook {
    public partial class BrowseIngredients : Form {
       public BrowseIngredients() { InitializeComponent(); }
       private void exitToolStripMenuItem_Click(object sender, EventArgs e) {
           if (MessageBox.Show("Exit Cook Book?", "Exit?", MessageBoxButtons.OKCanc

I am very much a beginner, so forgive me if I don’t understand the real problem!

Answer 1

Looking at the tutorial you are using I think I can see where you have gone wrong (and I don’t blame you the – tutorial is not entirely clear).

Based on this stage : http://www.homeandlearn.co.uk/csharp/csharp_s12p5.html

You will have in your Form Load method a statement something like:

string sql = "SELECT * From CookBookRecipes";
dataAdapt = new System.Data.SqlClient.SqlDataAdapter(sql, con);

However, the tutorial then tells you to add the following to get the data from the data adapter to into the dataset, but doesn’t actually show the code in context – and I suspect this is where you have gone wrong.

Immediately after the above lines you need to add this:

dataAdapt.Fill( dataRecipe, "CookBookRecipes" );

Then when you attempt to get the rows from dataRecipe.Tables[“CookBookRecipes”] you will not be returning a reference to a null object.