If the database connection string is hard-coded inCode, After compilation
If you want to change it, it is not easy to change it, so it is best to put it in the configuration file.
Winform is app. config
Webform is Web. config
<? XML version = "1.0" encoding = "UTF-8"?>
<Configuration>
<Configsections>
</Configsections>
<Connectionstrings>
<Add name = "windowsapplication11.properties. settings. mica_salemgnconnectionstring"
Connectionstring = "Data Source = mica-server; initial catalog = mica_salemgn; user id = sa"
Providername = "system. Data. sqlclient"/>
</Connectionstrings>
</Configuration>
You can use configurationmanager. connectionstring ["windowsapplication11.properties. settings. mica_salemgnconnectionstring"]. connectionstring;
Sqlconnection conn = new sqlconnection (the above string is in the middle );
Sqlconnection conn = new sqlconnection (system. configuration. configurationmanager. connectionstrings
["Windowsformsapplication3.properties. settings. testconnectionstring"]. connectionstring );