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string connString = "Your Connection String";

using (SqlConnection conn = new SqlConnection(connString)){

    conn.Open();

    string sql = "select DISTINCT column1, column2 from your_table";

    using (SqlCommand cmd = new SqlCommand(sql, conn))

    {

        using (SqlDataReader reader = cmd.executeReader())

        {

            while (reader.Read())

            {

                // 處理結(jié)果

            }

        }

    }

}

List<int> numbers = new List<int> { 1, 2, 3, 4, 4, 5, 5, 6 };

HashSet<int> uniqueNumbers = new HashSet<int>(numbers);

List<int> result = new List<int>(uniqueNumbers);

List<int> numbers = new List<int> { 1, 2, 3, 4, 4, 5, 5, 6 };

var uniqueNumbers = numbers.Distinct().ToList();

/// <summary>

/// 使用Linq的GroupBy()方法去重

/// </summary>

public static void GroupByDuplicate()

{

    var dataSource = new List<int>() { 1, 2, 3, 2, 5, 88, 99, 99, 100, 88, 30, 50, 15, 100, 99, 99, 2, 3 };

     //GroupBy()方法將原始集合中的元素進(jìn)行分組，根據(jù)指定的鍵或條件進(jìn)行分組。每個(gè)分組都會(huì)有一個(gè)唯一的鍵，通過(guò)將原始集合分組并選擇每個(gè)分組中的第一個(gè)元素，實(shí)現(xiàn)了去重的效果。

    var uniqueData = dataSource.GroupBy(item => item).select(group => group.First()).ToList();

     Console.WriteLine(string.Join(", ", uniqueData));

}

    public class ArrayDeduplication

    {

        /// <summary>

        /// 使用自定義的比較器和循環(huán)遍歷

        /// </summary>

        public static void CustomEqualityComparerDuplicate(){

            var dataSource = new List<int>() { 1, 2, 3, 2, 5, 88, 99, 99, 100, 88, 30, 50, 15, 100, 99, 99, 2, 3 };

            var uniqueData = new List<int>();

            foreach (var item in dataSource)

            {

                if (!uniqueData.Contains(item, new CustomEqualityComparer()))

                {

                    uniqueData.Add(item);

                }

            }

            Console.WriteLine(string.Join(", ", uniqueData));

        }

    }

            /// <summary>

    /// 自定義的比較器

    /// </summary>

    public class CustomEqualityComparer : IEqualityComparer<int>

    {

        public bool Equals(int x, int y){

            return x == y;

        }

         public int GetHashCode(int obj){

            return obj.GetHashCode();

        }

    }

/// <summary>

/// 直接循環(huán)遍歷去重

/// </summary>

public static void LoopTraversalDuplicate()

{

    var dataSource = new List<int>() { 1, 2, 3, 2, 5, 88, 99, 99, 100, 88, 30, 50, 15, 100, 99, 99, 2, 3 };

    var uniqueData = new List<int>();

    foreach (var item in dataSource)

    {

        //if (!uniqueData.Any(x => x == item))

        //if (!uniqueData.Exists(x => x == item))

        if (!uniqueData.Contains(item))

        {

            uniqueData.Add(item);

        }

    }

    Console.WriteLine(string.Join(", ", uniqueData));

}