I found the problem. It seems you can't bind the control to an integer and display a char. I think I should have known that already :(.

Sure you can. This is what combo boxes are all about. Combo boxes are particularly powerful controls because they enable you to display descriptive text from a lookup table while binding the control to its associated key value. This is possible only because the combo box has these two properties. Understanding the role each of them plays can be confusing, to say the least.

DisplayValue is the descriptive text that is displayed in the textbox portion of the control. This is what you see when the combo box is "closed." The combo's DisplayValue always comes from the first column of its RowSource. On the other hand, the combo's Value comes from whichever column is specified as its BoundColumn.

Typically, when the combo is in a grid, most people just set the column's Sparse property to false. This way, the descriptive text is displayed in all the grid rows.

The samples on oour web site offer some alternative solutions.