How to remove data from string builder

Hi i all having a requirement to delete particular data from a text file. I have written some code to get my exact data to remove but now i am little bit confused in removing that particular data can any one help me.

Initially this is my data in text file where i am storing to a Stringbuilder

101 111111111 1111111111110150105A094101                                                      

52201               1                   1         PPD1         111015111015   1111000020000001

6241110000251                00000000011              1                     1 0111000020000001

822000000100111000020000000000000000000000011                                  111000020000001

52251               1                   1         PPD1         011015111015   1111000020000002

6281110000251                0000000001开发者_高级运维1              1                     1 0111000020000002

822500000100111000020000000000010000000000001                                  111000020000002

9000002000001000000020022200004000000000001000000000001                                       

Now by using certain code i am getting the data to delete i.e assume i would like to delete from 5 to 8 which exists. I am storing this to another StringBuilder as follows

52251               1                   1         PPD1         011015111015   1111000020000002

6281110000251                00000000011              1                     1 0111000020000002

822500000100111000020000000000010000000000001                                  111000020000002

I would like to remove this from the main Stringbuilder i am having. Is this the correct process or if any better way let me know

You could use StringBuilder.Replace.

sb1.Replace(sb2.ToString(), "");

But better is to iterate over the data you wish to keep and serialize it to the file again. Take care to overwrite the file atomically if you don't want to risk losing data if the computer crashes while you are saving.