Resolve a placeholder from a single argument.

The Key value pair source handles a KeyValuePair<string, object> value. When the selector matches the pair's key, the source returns the pair's value. It is a lightweight way to supply one named value without building a dictionary.

The key must be a and the value must be an . A pair with any other key or value type, such as , is not handled and the next source is tried. A value resolves to an empty string. Use the nullable operator () to return an empty result instead of an error when the value is .

The comparison is case-sensitive, so the selector must match the key exactly.

// "a value"            Smart.Format("{placeholder}", new KeyValuePair<string, object>("placeholder", "a value"));

{placeholder}

KeyValuePair<string, object>("placeholder", "a value")

{placeholder}

KeyValuePair<string, object>("placeholder", null)