This is common requirement , you need to implement a If condition of If then else condition in a SSIS package flow. The example below illustrated it and implemented it with Precedence Constraints.
there is a table in sql data source , If any records exist in this table then a Data Flow must transfer this data, Else a process must start.
Create a variable in package scope name it cnt
Create an Execute SQL Task
Configure this task to return Select count(*) as cnt from table1 .
set the result set as Single row.
In Result Set tab, add a result set with name cnt and map it with variable User::cnt
Add a Data Flow Task.
Connect green line from Execute Process Task to this data flow task,this line called Precedence Constraint and show the flow of tasks in package.
right click on this line and select Edit
In Precedence Constraint Editor, set evaluation operation as Expression
in Expression box write this : @cnt>0
add a Execute process task,
connect green line from execute process task to this new task , right click on line and select edit
set evaulation operation as Expression, and expression box : @cnt<=0
run the package.
This is overall plan schema: