A simple expression is a reference or a pointer to an item in one of the collections, for example, a field from the dataset. A simple expression is visualized in the textbox using ([]) brackets.
A complex expression is a combination of simple expressions and operators or functions. As soon as you use a complex expression for the Value property of a textbox, the textbox will contain <<Expr>> when you look at it in the report layout, as you can see in the following example:
For this reason, I recommend that you give every textbox a proper name, so that you can see in its properties what it actually contains, as in the following example:
Note
This is especially important when you are developing a document report. In this type of report there are many fields, and it can get confusing to edit and customize if you are asked to change the context of a textbox. By applying proper names, you can use the property drop-down or document outline to quickly locate...