César was a brother of Xavier de Cock. He studied at Ghent art school. Originally he trained as a musician and singer, but then became deaf and turned to painting. He worked for a long time in France, where he studied with Charles Daubigny and François Louis Français and made friends with Jean-Baptiste Corot, Rousseau, Diaz and Troyon. He lived in Deurle during the war of 1870 and then, after the Paris Commune came to an end, at Gasny in the Eure. He settled permanently in Ghent in 1880. He showed regularly in the Paris Salons, winning medals in 1867 and 1869.

He painted in Barbizon, in Veule and in the Meudon woods, then in the Lys country. His landscapes remind one of the style of his teacher Daubigny, but also of the nuanced greens of Hobbema's woodlands, and they gradually come closer to Impressionism.

Museum and Gallery Holdings

Antwerp: Forest View, St-Germain-en-Laye; Banks of the River Epte in Gasny (Eure)
Béziers: The Stream; Banks of a Flemish River
Ghent: The Road to Patijntje
Grenoble: Watercress at Veule
Helsinki: Sunny Morning in the Forest
Le Havre: Banks of a Flemish River
Liège: Landscape, in a Forest
Lille: Landscape
Limoges: In the Forest, Autumn Landscape
London (Victoria and Albert Mus.): River at Gasny
Paris (Louvre): Road to La Garenne
Rheims (MBA): Path under Trees; Line Fishermen