How to get Values by Row based on Column Name

Assume that we are dealing with the following data frame and we want to add another column that returns the values of the columns as noted at the selection column:

set.seed(5)
df<-as.data.frame(matrix(sample(1:100,12),ncol=3))
df$Selection<-c("V1","V3","V2","V3")

df

    V1 V2 V3 Selection
1 66 41 19        V1
2 57 85  3        V3
3 79 94 38        V2
4 75 71 58        V3

We apply the following trick:

df$Value<-as.numeric(df[cbind(seq_len(nrow(df)), match(df$Selection,names(df)))])

df

Output:

  V1 V2 V3 Selection Value
1 66 41 19        V1    66
2 57 85  3        V3     3
3 79 94 38        V2    94
4 75 71 58        V3    58