using Yorukatsu038.Questions;
using Yorukatsu038.Extensions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace Yorukatsu038.Questions
{
    /// <summary>
    /// ABC096 C
    /// </summary>
    public class QuestionB : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var hw = inputStream.ReadIntArray();
            var h = hw[0];
            var w = hw[1];

            var canvas = new char[h][];
            for (int i = 0; i < h; i++)
            {
                canvas[i] = inputStream.ReadLine().ToCharArray();
            }

            for (int row = 0; row < h; row++)
            {
                for (int column = 0; column < w; column++)
                {
                    if (canvas[row][column] == '#')
                    {
                        var isOk = (row > 0 && canvas[row - 1][column] == '#') ||
                            (row < h - 1 && canvas[row + 1][column] == '#') ||
                            (column > 0 && canvas[row][column - 1] == '#') ||
                            (column < w - 1 && canvas[row][column + 1] == '#');
                        if (!isOk)
                        {
                            yield return "No";
                            yield break;
                        }
                    }
                }
            }

            yield return "Yes";
        }
    }
}


namespace Yorukatsu038
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionB();    // 問題に合わせて書き換え
            var answers = question.Solve(Console.In);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
        }
    }
}

#region Base Classes

namespace Yorukatsu038.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);
    }

}

#endregion

#region Extensions

namespace Yorukatsu038.Extensions
{
    internal static class TextReaderExtensions
    {
        internal static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        internal static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        internal static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        internal static string ReadString(this TextReader reader) => reader.ReadLine();

        internal static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        internal static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        internal static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        internal static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);
    }
}

#endregion

Measured memory_bytes: 13396