How to upload big file on server by using code?

In Web.config file

<httpRuntime 
executionTimeout = "number" 
maxRequestLength = "number"
requestLengthDiskThreshold = "number" 
useFullyQualifiedRedirectUrl = "[True|False]" 
minFreeThreads = "number" 
minLocalRequestFreeThreads = "number" 
appRequestQueueLimit = "number" 
enableKernelOutputCache = "[True|False]" 
enableVersionHeader = "[True|False]" 
apartmentThreading = "[True|False]" 
requireRootedSaveAsPath = "[True|False]" 
enable = "[True|False]" 
sendCacheControlHeader = "[True|False]" 
shutdownTimeout = "number" 
delayNotificationTimeout = "number" 
waitChangeNotification = "number" 
maxWaitChangeNotification = "number" 
enableHeaderChecking = "[True|False]" />