My blog title is proved once again.

A small application I’m working on at the moment needs to present the user some colours and the ability to change them and save changes. So, I decided to use a DataGridView with a custom colour picker column (that’s a separate story I think). The colours are stored in the database table as integers in ARGB format. So, to present them, I need to convert them to System.Drawing.Color.

I have a piece of code like that

public DataTable GetColours()
{
 // snip      
 DataTable colors = new DataTable();      
 // snip      
 colors.Columns.Add(MyColourTypes.BackGroundColour.ToString());
 // snip      
 DataRow newRow = colors.NewRow();
 int bgColour;
 if (int.TryParse(iMyColourValue.ToString(), out bgColor))
 {
  newRow[MyColourTypes.BackGroundColour.ToString()] = Color.FromArgb(bgColor);      
 }
 else
 {
  newRow[MyColourTypes.BackGroundColour.ToString()] = Color.Empty;      
 }
}

So if a value in the database is int, I convert it to Color and add to DataTable, otherwise I put Color.Empty in the DataTable (Colours can be nulls).

However, my DataGridView complained about the invalid cast exception on the line

Color lclcolor = (Color)value;

Where value is the entry from my DataTable.

So I thought that the colours in the database may be not “known colours” and spent at least an hour searching for a “proper” way to convert a colour from integer to System.Drawing.Color. It took a while till I noticed in the watch window that even when the value is “Color[Black]” the debugger refuses to unbox it as a System.Drawing.Color. Further investigation proved, that value is indeed not a Color structure, but more looks like a string. Another minute of intense thinking, and I replace

colors.Columns.Add(MyColourTypes.BackGroundColour.ToString());

with

colors.Columns.Add(MyColourTypes.BackGroundColour.ToString(), typeof(Color));

A rainbow of colours appear in my DataGridView.

Moral: when you want to store something more complex than a string or an int in a DataTable, don’t forget to tell the table what type of object you want to store.

Good thing: I learned a few things about converting colours between different format