LeetCode: Pascal's Triangle C#
Something I ran into while making my own implementation:

After 34 rows, the highest number in the row will be two 1166803110s. Adding these for row 35 exceeds the maximum value for ints, resulting in integer-overflow.

You might consider putting the line that does the addition into a checked block, so that an OverflowException is properly thrown:

for (int j = 0; j &lt; prevRow.Count - 1; j++)
{
     checked 
     {
         row.Add(prevRow[j] + prevRow[j + 1]);
     }
}


As mentioned in the comments, the values in the rows grow almost exponentially. This means that switching from int to long as datatype in the lists will only roughly double the amount of rows that can be supported before these too overflow.