ASP.NET Request Headers key/value pairs.

Platforms Supported: All

Introduced in NLog.Web 4.9 and NLog.Web.AspNetCore 4.9

${aspnet-request-headers:headerNames=String[]:outputFormat=Enum
    :itemSeparator=String:valueSeparator=String
    :valuesOnly=Boolean}

• items - Header key name(s). A list of keys can be passed as comma separated values, e.g.: Key1,Key2 (Not specified means all)

  Introduced with NLog.Web / NLog.Web.AspNetCore v5.2.1, and replaces the headerNames-option.

• exclude - Header key names to be excluded. A list of keys can be passed as comma separated values, e.g.: Key1,Key2

• outputFormat - Renders as flat string or as JSON. Default: Flat.
  • Flat - Key-value-pair as standard string
  • JsonArray - Key-value-pair in JSON-array (Introduced with NLog 5.0, replaces now obsolete Json)
  • JsonDictionary - Key-value-pair as JSON-dictionary. (Introduced with NLog 5.0, replaces now obsolete singleAsArray)
• itemSeparator - Separator between items. Default: ,. Only applies when OutputFormat is Flat.
• valueSeparator - Separator between value and key. Default: =. Only applies when OutputFormat is Flat.
• ValuesOnly - Only render the values of the key/value pairs. Default: false.
• LowerCaseKeys - Convert Keys to lowercase. Default: false.

  Introduced in NLog.Web / NLog.Web.AspNetCore v5.1.1

Use this layout renderer to log the value of the specified headers(s) stored in the ASP.NET Request Headers collection.

In C# code:

Request.Headers["key1"] = "value1";
Request.Headers["id"] = "d4b20a34-6231-4201-83a6-c72599e41164";

${aspnet-request-headers:HeaderNames=key1}

Will print:

"key1=value1"

${aspnet-request-headers:HeaderNames=key1,id}

Will print:

"key1=value1,id=d4b20a34-6231-4201-83a6-c72599e41164"

${aspnet-request-headers:HeaderNames=key1:OutputFormat=JSON}

Will print:

[{"key1":"value1"}]

${aspnet-request-headers:HeaderNames=key1,id:OutputFormat=JSON}

Will print:

[{"key1":"value1","id":"d4b20a34-6231-4201-83a6-c72599e41164"}]

${aspnet-request-headers:HeaderNames=key1:OutputFormat=JsonDictionary}

Will print:

{"key1":"value1"}

${aspnet-request-headers:HeaderNames=key1:ValuesOnly=true}

Will print:

"value1"

${aspnet-request-headers:HeaderNames=key1:OutputFormat=JSON:ValuesOnly=true}

Will print:

["value1"]

${aspnet-request-headers:HeaderNames=key1,id:OutputFormat=JSON:ValuesOnly=true}

Will print:

["value1","d4b20a34-6231-4201-83a6-c72599e41164"]