# HttpKnownHeaderNames.IfUnmodifiedSince

Kind: Field  
Namespace: `Sisk.Core.Http`  
Assembly: `Sisk.Core.dll`  
Source: https://docs.sisk-framework.org/api/Sisk.Core.Http.HttpKnownHeaderNames.IfUnmodifiedSince.html

## IfUnmodifiedSince {#Sisk_Core_Http_HttpKnownHeaderNames_IfUnmodifiedSince}

The HTTP If-Unmodified-Since header.

Used to make a conditional request, allowing the client to specify that the resource should only be returned if it has not been modified since the given date.

```csharp
public const string IfUnmodifiedSince = "If-Unmodified-Since"
```

### Field Value

[string](https://learn.microsoft.com/dotnet/api/system.string)