STNumGeometries (geography Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns the number of geometries that make up a geography instance.
Syntax
.STNumGeometries ( )
Return Types
SQL Server return type: int
CLR return type: SqlInt32
Remarks
This method returns 1 if the geography instance is not a MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection instance, or 0 if the geography instance is empty.
Examples
The following example creates a MultiPoint instance and uses STNumGeometries() to find out how many geometries the instance contains.
DECLARE @g geography;
SET @g = geography::STGeomFromText('MULTIPOINT((-122.360 47.656), (-122.343 47.656))', 4326);
SELECT @g.STNumGeometries();