As described by the The Map Data Model topic the purpose of the Nevron Map for SSRS report item is to display data that originates from your report data and "map" it to certain geospatial data. To do that there is a data cell associated with each map layer. When the report item is processed at runtime, that data cell expands to a data table, which has as many rows, as defined by the row data groupings. The Layer - Data Cell tab lets you specify the data that is contained inside each data cell at runtime. This includes data fields, appearance and action information.
Data Fields are [name:value] pairs where the Name of the data field is static (i.e. a constant value), while the value is usually obtained by an expression. Data Fields define the so called layer data table, that is obtained from the report data. There are two reasons for which you need to make a data field:
1. If you want to perform data binding on that data field.
2. If you want to display that data field as shape value or text.
Most of the time you will use the Fill Rule of the layer to define the map layer shapes appearance. However in certain cases you may need to apply custom filling and outline to the map layer shapes, that are based on the report data. This is achieved with the Data Cell - Appearance tab which lets you define dynamic appearance for the data bound items in the map. The tab has the following properties:
Visible - determines the visibility of the map shape created for the data cell. You will typically use expressions to specify conditional visibility of the map shapes.
Use Custom Appearance - when checked, you are able to specify the fill and stroke of each map layer shape individually, by entering expressions for the shape Fill, Border and Text properties.
Fill - embeds the Fill Style FX Editor. The expressions for the shape fill are recorded in the data cell, so when evaluated each shape may have different filling, based on the result of the expressions evaluation. Enabled only if Use Custom Appearance is set to true.
Border - embeds the Stroke Style FX Editor. The expressions for the shape border are recorded in the data cell, so when evaluated each shape may have different border, based on the result of the expressions evaluation. Enabled only if Use Custom Appearance is set to true.
Text - embeds the Text Style FX Editor. The expressions for the shape text are recorded in the data cell, so when evaluated each shape may have different text style, based on the result of the expressions evaluation. Enabled only if Use Custom Appearance is set to true.