Fetching specific values from a database using user input array. It works for single items but not for a list of itemids

Question

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C#

private void button2_Click(object sender, EventArgs e)
        {
            connection = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\Login App\SmartShop.accdb");
            command = connection.CreateCommand();

            txtbox2.Clear();

            try
            {
                connection.Open();
                OleDbCommand cmd = new OleDbCommand();
                cmd.Connection = connection;
                string query = "Select * from Items WHERE ItemID = '"+strarray+"'";
                cmd.CommandText = query;

                OleDbDataAdapter da = new OleDbDataAdapter(cmd);
                DataTable dt = new DataTable();

                da.Fill(dt);

                connection.Close();

                dataGridView1.DataSource = dt;


            }
            catch (Exception ex)
            {
                MessageBox.Show("Error" + ex);

            }     
            
        }

Posted 7-May-15 0:27am

Dakota335

Updated 7-May-15 0:39am

CHill60

v2

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Comments

sashje- 7-May-15 6:37am

Given that strArray is of type string[], you need to add a clause foreach of the items.. so you can decide if you want to use OR or AND between the items in the array...

Dakota335 7-May-15 7:05am

It says syntax error/ missing operator @ ItemID IN(,123,....)

Richard Deeming 7-May-15 8:09am

Your code is vulnerable to SQL Injection[^].

NEVER use string concatenation to build a SQL query. ALWAYS use a parameterized query.

3 solutions

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CHill60 · Accepted Answer · 2015-05-07T00:44:00

Solution 2

Change

SQL

string query = "Select * from Items WHERE ItemID = '"+strarray+"'";

to

SQL

string query = "Select * from Items WHERE ItemID IN (" + String.Join(",", strarray) + ")";

[Edit] - If the contents of strarray are strings then you need to surround them with single quotes e.g.

C#

string query = "Select * from Items WHERE ItemID IN (" + String.Join(",", Array.ConvertAll(strarray, z => "'" + z + "'")) + ")";

I note that your comment said

Quote:
syntax error/ missing operator @ ItemID IN(,123,900C,....)

That initial comma between the brackets is happening because you have not populated the first element in the array - remember arrays are zero-based so the first element is in [0], the second is in [1], etc. Take care when you are populating the array.

Posted 7-May-15 0:44am

CHill60

Updated 7-May-15 1:34am

v2

Comments

Dakota335 7-May-15 6:52am

This strarray is actually an array created by the user input through a textbox. There is always an error when I try to display the results. :(

CHill60 7-May-15 7:08am

What error? Are you validating the text box input? - I presume ItemID is integer and not varchar.

Dakota335 7-May-15 7:11am

Thanks for your help.
Nah, ItemID is a string like "099C12". The user inputs the id in a textbox at button clicks. I store that in an array. And therefore I want to display the rows matching the IDs in the array.
t says syntax error/ missing operator @ ItemID IN(,123,900C,....)

CHill60 7-May-15 7:34am

I've updated my solution

Dakota335 7-May-15 7:49am

Omg! That really solved my problem. Thanks a ton :)
Finally my project can progress now

CHill60 7-May-15 8:13am

Good - but please note the comments from Richard Deeming - the code is (very)vulnerable to SQL Injection (see the link in Richard's comment) as the array is constructed from user input.

Richard Deeming 7-May-15 8:10am

That code is vulnerable to SQL Injection[^].

CHill60 7-May-15 8:15am

I completely agree and have pointed out your comment to the OP. A virtual 5 to you.

Dakota335 8-May-15 1:59am

Yep that completely sorts out the problem :)
Great!!!

Maciej Los 14-May-15 7:52am

+5!

CHill60 14-May-15 7:52am

Cheers!

Richard Deeming · Accepted Answer · 2015-05-07T02:21:00

Further to Chill60's answer, you need to use a parameterized query to avoid SQL Injection[^].

It's not quite as simple with an array parameter, but it's still fairly easy:

C#

private void button2_Click(object sender, EventArgs e)
{
    using (var connection = new OleDbConnection(@"Provider=Microsoft.ACE.OLEDB.12.0;Data Source=D:\Login App\SmartShop.accdb"))
    using (var command = connection.CreateCommand())
    {
        command.CommandType = CommandType.Text;

        var sb = new System.Text.StringBuilder("SELECT * FROM Items WHERE ItemID IN (");
        for (int index = 0; index < strarray.Length; index++)
        {
            if (index != 0) sb.Append(',');

            // OleDb doesn't use named parameters, so only the order matters here:
            command.Parameters.AddWithValue("@p" + index, strarray[index]);
            sb.Append('?');
        }
        sb.Append(')');

        command.CommandText = sb.ToString();

        var da = new OleDbDataAdapter(cmd);
        var dt = new DataTable();
        da.Fill(dt);

        dataGridView1.DataSource = dt;
    }
}

OriginalGriff · Accepted Answer · 2015-05-07T00:43:00

Solution 1

Try using a IN clause:

SQL

SELECT * FROM Items WHERE ItemId IN (1, 2, 3, 4, 666, 777)

Posted 7-May-15 0:43am

OriginalGriff