C＃和SQL Server：索引超出了数组的范围

Question

I'm trying to get data from the SQL Server database but the error state that

System.IndexOutOfRangeException: Index was outside the bounds of the array.

This is my table

TourDisplay

My code:

SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=....;Integrated Security=True;Connect Timeout=30;User Instance=True;");

SqlCommand cmd = new SqlCommand();
SqlDataReader dtr;

protected void Page_Load(object sender, EventArgs e)
{
    cmd.Connection = conn;
    conn.Open();

    cmd.CommandText = "select BicycleType from TourDisplay order by TDateTime asc";

    dtr = cmd.ExecuteReader();
    bool temp = false;

    while (dtr.Read())
    {
        TBBicycleType.Text = dtr.GetString(0);
        TBBicycleType2.Text = dtr.GetString(1);
        temp = true;
    }     
}

As you can see, the code should be fine because I got 3 data inside the table but I'm having problem on GetString(1) .

Answer 1

It appears that in your select statement, you are selecting ONE column, but in the reader, you're trying to select two.

EXAMPLE: SELECT Id, BicycleType FROM TourDisplay ORDER BY TDateTime

Please either add another column to your select statement, or remove the second selector from the reader:

TBBicycleType2.Text = dtr.GetString(1);

Edit per comment

It appears that you may be trying to set two different buttons, using the first two results from your query with this while reader loop. I'd tweak it a little as follows:

protected void Page_Load(object sender, EventArgs e)
{
    cmd.Connection = conn;
    conn.Open();
    cmd.CommandText = "SELECT BicycleType FROM TourDisplay ORDER BY TDateTime";
    dtr = cmd.ExecuteReader();
    bool temp = false;

    // Added this variable.  name it anything you like.
    bool isFirstItem = true;
    while (dtr.Read())
    {
        // After the first loop iteration, isFirstItem will be set to false
        if (isFirstItem)
        {
            TBBicycleType.Text = dtr.GetString(0);
            isFirstItem = false;
        }
        // All consequent iterations of the loop will set the second 
        // item's 'Text' property.  So if you have only two rows, it 
        // will be the second row.  If you have 20 rows, it will be the 20th row.
        else
            TBBicycleType2.Text = dtr.GetString(0);

        temp = true;
    }     
}

Although, if you're just setting two buttons using a while loop and from the database, I'd rethink your design a little?

Edit 2 per changes to the OP mentioning 3 total rows in the database

protected void Page_Load(object sender, EventArgs e)
{
    cmd.Connection = conn;
    conn.Open();
    cmd.CommandText = "SELECT BicycleType FROM TourDisplay ORDER BY TDateTime";
    dtr = cmd.ExecuteReader();

    // Again, I'd rethink your design, but if you're just playing
    // around this should be fine
    int count = 0;
    while (dtr.Read())
    {
        switch (count)
        {
            case 0:
                TBBicycleType.Text = dtr.GetString(0);
                break;
            case 1:
                TBBicycleType2.Text = dtr.GetString(0);
                break;
            // Add whatever you want to do with the third one here
            // case 2:
            //     TBBicycleType3.Text = dtr.GetString(0);
            //     break;
         }
        count++;
    }     
}

Answer 2

The index is indeed out of bounds. Since you're trying to get the second column on dtr.getString(1). To fix, remove the dtr.getString(1).

In each iteration, dtr.GetString(0) gets the next row of BicycleType. So first iteration, TBBicycleType.Text = "Time Trial". Second iteration, TBBicycleType.Text = "MTB". and so on.

SqlConnection conn = new SqlConnection(@"Data Source=.\SQLEXPRESS;AttachDbFilename=....;Integrated Security=True;Connect Timeout=30;User Instance=True;");
SqlCommand cmd = new SqlCommand();
SqlDataReader dtr;


protected void Page_Load(object sender, EventArgs e)
{
    cmd.Connection = conn;
    conn.Open();
    cmd.CommandText = "select BicycleType from TourDisplay order by TDateTime asc";
    dtr = cmd.ExecuteReader();
    bool temp = false;
    while (dtr.Read())
    {
        TBBicycleType.Text = dtr.GetString(0);
        temp = true;
    }     
}