You haven't told the DataGridViewColumn what to bind to.
Normally you bind to a public property of the bound data type. In this case your data type is long
which does not have an appropriate property to bind to.
Wrap your long
in a custom class and expose it as a public property.
public class Data
{
public long Value { get; set; }
}
Bind your column to the Value
property. You can do this in the designer, but here is the code:
Column1.DataPropertyName = "Value";
Now instead of long
you use Data
:
ProjectIDs = new BindingList<Data>();
...
long temp = long.Parse(textBox1.Text);
ProjectIDs.Add(new Data { Value = temp });