interface type method parameter implementation c#

interface IDBBase {

     DataTable getDataTableSql(DataTable curTable,IDbCommand cmd);
     ...
}

class DBBase : IDBBase {

     public DataTable getDataTableSql(DataTable curTable, SqlCommand cmd) {
         ...
     }
}

class DBBase : IDBBase {

    DataTable IDBBase.getDataTableSql(DataTable curTable, IDbCommand cmd) {
         return getDataTableSql(curTable, (SqlCommand)cmd); // of course you should do some type checks
     }

     public DataTable getDataTableSql(DataTable curTable, SqlCommand cmd) {
         ...
     }
}

interface IDBClass<T> where T:IDbCommand
{
    void Test(T cmd);
}

class DBClass:IDBClass<SqlCommand>
{
    public void Test(SqlCommand cmd)
    {
    }
}

interface Interface1 { }
class Class1 : Interface1 {}

interface Interface2 { void Foo(Interface1 i1);}
class Class2 : Interface2 {void Foo(Class1 c1) {}}

interface Interface2 { void Foo(Interface1 i1);}
class Class2 {void Foo(Class1 c1) {}}

interface Interface2 { void Foo(Interface1 i1);}
class Class2:Interface2 {void Foo(Class1 c1) {}}

genClass"<"typeOj">"

 {

    typeOj instOj;

    public  genClass(typeOj o)


    {      instOj=o  ;    }


    public typeOj getType()

    {        return instOj;    }


interface IDBBase
{

     DataTable getDataTableSql(DataTable curTable,genClass<idcommand> cmd);
     ...
}

class DBBase : IDBBase
{

     public DataTable getDataTableSql(DataTable curTable, genClass<SqlCommand> cmd)
 {
         ...
     }

}