Assuming you're interested in current (or most recent) daily, weekly, monthly or yearly high and low, I suggest you use Eikon .NET SDK. Follow the link below for the tutorial on retrieving real-time market data using this API.
To figure out field names you need to use type in the RIC into a Quote app in Eikon application. Then either hover the mouse pointer over the field you're interested in in the quote display. The tooltip will show the RIC and the field name followed by something else you can ignore. Or click on Display All Fields button in the Quote app toolbar, which will show you the raw view of the real-time record as the vector of field name/value pairs.
For composite spot exchange rate RICs such as <EUR=> use HIGH_1 and LOW_1 for daily high/low, WEEK_HIGH and WEEK_LOW for weekly, MONTH_HIGH and MONTH_LOW for monthly, YRHIGH and YRLOW for yearly.
If you need something else, such as perhaps timeseries or high/low for a specific period of time, then please elaborate on what you're after.