You can do it with:
```
var queryableResultItems = context.GetQueryable<GlobalSearchResultItem >()
                    .Where(expression)
                    .OrderByDescending(x => x["termfreq(content_t, \""+ term+ "\")"])
```

But I suggest you to setup logic that you need on Solr side. Sorl sorts the results based on the relevancy of the term present in the field OOTB (it uses **tf-idf** algorithm to calculate scoring).

You should check query analizer of your field type in managed-schema (your field should be **tokenized**):
```
<analyzer type="query">
      <tokenizer class="solr.WhitespaceTokenizerFactory"/>
      ...
    </analyzer>
```

[![enter image description here][1]][1]


You can check it in Solr by adding "**score**" in **fl** textbox. You can also see how scoring is calculating by checking **debugQuery**:
[![enter image description here][2]][2]


As you can see, Solr uses **termFreq** OOTB while scoring:
[![enter image description here][3]][3]


  [1]: https://i.sstatic.net/yiBRL.png
  [2]: https://i.sstatic.net/k84Mr.png
  [3]: https://i.sstatic.net/Pkk6Y.png