c# - I'm editing an application that loads data from a database, but it runs slower as it continues running -

it's not well-designed application, gets job done gets used. on past week, i've been making modifications it. i've added , removed features. gets data sql table. depending on run, data can upwards of 20,000 rows!

i thinking trying load 500 rows application @ time because when there 500 rows process, takes seconds, not minutes. working pdfs, , may part of issue too, figure shouldn't hard implement.

the thing though, i'm not sure how implement it. idea limit query 0 500, increment limit. main loop checks if row returned null. how know if row returned null because it's last row of table not last row of chunk?

edit: apologize. query quick. however, during operations pdf files, stored locally on filesystem application running on, speed of these operations gets slower. thinking fact pulling 20,000 rows of data application , having loop through locally causing slow-down. may wrong, why wanted implement paging. running program on 500 rows fast. both pull in of rows @ start of program perform operations on pdfs using library (i.e. placing row data on page). each row corresponds page in pdf, fact pdf getting large may slowing things down, paging working report back. more of application performance issue time progresses.

with limited information can refer sql paging resource commonly used technique developers limit number of records retrieved.

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