Question

I am working on a site that users can add and delete videos from a list.
All the adding and removing is done with checkboxes. I can add multiple videos at a time but when I try to delete more than one of them at a time from the list, it gives me this error:

Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

However when there are no issues removing one at a time. Also when I get the error and go back the checked videos are gone.
This is in C# ASP.NET and I am not sure where the error is, but I believe it to be in the btnDeleteVideo_Click event. I am showing the other event (btnAddVideo_Click) as reference if needed. I can remove that if it would help. I am new to stackoverflow so I am sorry if this is too much or too little info.

Here is the code for both the adding and removing events:

protected void btnAddVideo_Click(object sender, EventArgs e)
{

    foreach (GridViewRow gvr in GridView3.Rows)
    {
        CheckBox chkItem = (CheckBox)gvr.FindControl("cbAdd");
        if (chkItem.Checked)

        {
            String sRecID = GridView3.DataKeys[gvr.RowIndex].Value.ToString();
            Session["videorecid"] = sRecID;
            SqlDataSource2.Insert();
            SqlDataSource2.SelectCommand = "SELECT * FROM dealervideo inner join videos on videos.RecID = dealervideo.VideoRecID inner join dealers on dealers.RecID = dealervideo.DealerRecID where dealers.RecID = " + hidRecID.Value;
            GridView2.DataBind();
        }
    }
    GridView2.DataBind();
}

protected void btnDeleteVideo_Click(object sender, EventArgs e)
{

    foreach (GridViewRow gvr in GridView2.Rows)
    {
        CheckBox chkItem = (CheckBox)gvr.FindControl("cbDelete");
        if (chkItem.Checked)
        {
            String sRecID = GridView2.DataKeys[gvr.RowIndex].Value.ToString();
            Session["videorecid"] = sRecID;
            SqlDataSource2.Delete();
            SqlDataSource2.SelectCommand = "SELECT * FROM dealervideo inner join videos on videos.RecID = dealervideo.VideoRecID inner join dealers on dealers.RecID = dealervideo.DealerRecID where dealers.RecID = " + hidRecID.Value;
            GridView2.DataBind();
        }
    }
}

Answer 1

The problem is the logic of btnDeleteVideo_Click.

Imagine you have 5 items in your list, numbered 0 to 4, and you try to delete 2 at once.

Your code above now loops through all five rows. When it gets to the first deletion, it removes a row by deleting from the data source and rebinding.

It now continues through the loop until it finds the second item marked from deletion – except that your grid now contains one less row since you deleted and rebound.

So the line String sRecID = GridView2.DataKeys[gvr.RowIndex].Value.ToString(); will have a tendency to explode as the original RowIndex may now be higher than the actual number of rows.

A better approach would be to work out all the rows you want to delete by loopin as you are, but only delete and rebind at the end.