Similar solution in C#:

static long ArrayManipulation(int n, int[][] queries) {    
    var additions = new long[n + 1];
    foreach (var query in queries) {
        var start = query[0];
        var end = query[1];
        var valueToAdd = query[2];
        additions[start] += valueToAdd;
        if (end + 1 < additions.Length)
            additions[end + 1] -= valueToAdd;            
    }        
    long sum = 0;
    long max = 0;
    for (var x = 1; x < additions.Length; x ++) {
        sum += additions[x];
        max = sum > max ? sum : max;
    }
    return max;
}