What operator checks whether a field is set to a value in textbox filtering?

The operator that checks whether a field is set to a specific value in textbox filtering is the percent sign, which is used as a wildcard. However, in the context of filtering data within textboxes, the equals sign functions to determine if a field matches a specified value.

Using the equals sign allows you to explicitly check if a field is equal to a certain value, making it ideal for situations where you want to confirm an exact match. This operator is not just for indicating equality; its usage in filtering ensures that the field actually holds the value specified in the filtering criteria, which is essential for accurate data retrieval and display.

The other options do not serve the same purpose in the context of filtering. The underscore character, for example, is often used for a specific type of string operation, while the tilde may refer to other functions or characteristics in programming contexts. The percent sign, while often associated with wildcards, pertains to broader searching and may not provide the specific equality match that the equals sign does in this scenario.