Problem1 : You are trying to convert the null value from one of the cells into String.
Solution1 : before converting cell value into String do a null check.
Problem 2: you are using Console.WriteLine() method to display each cell value.so that it prints each cell value in a new Row/Line.
Solution 2: you need to use Console.Write() method instead of Console.WriteLine() to print cell values, and once after printing all cell values from a given row you need to use Console.WriteLine() to print new line.
Suggestion: you don't need to declare the string variable value each time in a for loop, so you can move the string variable declaration out of the loop.
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