Report Builder functions - First function in a paginated report (Report Builder)
Applies to: 
Microsoft Report Builder (SSRS)
Power BI Report Builder
Report Designer in SQL Server Data Tools
Returns the first value in the given scope of the specified expression in a paginated report.
Note
You can create and modify paginated report definition (.rdl) files in Microsoft Report Builder, Power BI Report Builder, and in Report Designer in SQL Server Data Tools.
Syntax
First(expression, scope)
Parameters
expression
(Variant or Binary) The expression on which to perform the aggregation, for example, =Fields!FieldName.Value.
scope
(String) Optional. The name of a dataset, group, or data region that contains the report items to which to apply the aggregate function. If scope is not specified, the current scope is used.
Return Type
Determined by the type of expression.
Remarks
The First function returns the first value in a set of data after all sorting and filtering have been applied at the specified scope.
The First function cannot be used in group filter expressions with anything except the current (default) scope.
You can also use First in a page header to return the first value from the ReportItems collection for a page in order to produce dictionary-style headings that display the first and last entries on a page.
The value of scope must be a string constant and cannot be an expression. For outer aggregates or aggregates that do not specify other aggregates, scope must refer to the current scope or a containing scope. For aggregates of aggregates, nested aggregates can specify a child scope.
Expression can contain calls to nested aggregate functions with the following exceptions and conditions:
Scope for nested aggregates must be the same as, or contained by, the scope of the outer aggregate. For all distinct scopes in the expression, one scope must be in a child relationship to all other scopes.
Scope for nested aggregates cannot be the name of a dataset.
Expression must not contain First, Last, Previous, or RunningValue functions.
Expression must not contain nested aggregates that specify recursive.
For more information, see Aggregate Functions Reference (Report Builder and SSRS) and Expression Scope for Totals, Aggregates, and Built-in Collections (Report Builder and SSRS).
For more information about recursive aggregates, see Creating Recursive Hierarchy Groups (Report Builder and SSRS).
Example
The following code example returns the first product number in the Category group of a data region:
=First(Fields!ProductNumber.Value, "Category")