Transact SQL :: Delete All Records Using FOREIGN KEY Constraints If Main Table Entity Is Deleted

How to delete records from multiple tables if main table’s entity is deleted as constraints is applied on all..There is this main table called Organization or TblOrganization.and this organization have branches which are in Brach table called tblBranch and this branch have multiple applications let say tblApplication and these application are used by multiple users called tblUsers.What I want is: when I delete the Organization All branches, application and users related to it must be deleted also.How I can apply that on a button click in asp.net web forms..Right now this is my delete function which is very simple

Public void Delete(int? id){
var str=”DELETE FROM tblOrganization WHERE organizationId=”+ id ;
}
And My tables LOOK LIKE this
CREATE TABLE tblOrganization
(
OrganizationId int,
OrganizationName varchar(255)

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