自己整理的的数据操作DbHelper

using System.Data;
using System.Data.SqlClient;
using System.Configuration;

namespace WindowsFormsApp3
{
    public class DbHelper
    {
        private static string connStr = ConfigurationManager.ConnectionStrings["Demo"].ToString();

        /// <summary>
        /// 根据Sql语句返回Table类型数据
        /// </summary>
        /// <param name="sql">查询Sql语句</param>
        /// <returns>Table</returns>
        /// <SqlParameter>SqlParameter</SqlParameter>
        public static DataTable GetDataTable(string sql, SqlParameter[] sqlParameter = null)
        {
            DataSet ds = new DataSet();
            using (SqlConnection sqlConn = new SqlConnection(connStr))
            {
                sqlConn.Open();
                if (sqlConn.State == ConnectionState.Open)
                {
                    using (SqlCommand cmd = new SqlCommand(sql, sqlConn))
                    {
                        if (sqlParameter != null && sqlParameter.Length > 0)
                            cmd.Parameters.AddRange(sqlParameter);
                        SqlDataAdapter da = new SqlDataAdapter(cmd);
                        da.Fill(ds);
                    }
                }
            }
            return ds.Tables[0];
        }

        /// <summary>
        /// 查询数据库是否存在数据
        /// </summary>
        /// <param name="sql">查询Sql语句</param>
        /// <param name="sqlParameter">查询参数</param>
        /// <returns>存在返回True，不存在返回False</returns>
        public static bool DataIsHasRows(string sql, SqlParameter[] sqlParameter = null)
        {
            bool HasRows = false;
            using (SqlConnection sqlConn = new SqlConnection(connStr))
            {
                sqlConn.Open();
                if (sqlConn.State == ConnectionState.Open)
                {
                    using (SqlCommand cmd = new SqlCommand(sql, sqlConn))
                    {
                        if (sqlParameter != null && sqlParameter.Length > 0)
                            cmd.Parameters.AddRange(sqlParameter);
                        using (SqlDataReader dr = cmd.ExecuteReader())
                        {
                            if (dr.HasRows)
                            {
                                HasRows = true;
                            }
                        }
                    }
                }
            }
            return HasRows;
        }
        /// <summary>
        /// 执行Sql语句返回受影响行数
        /// </summary>
        /// <param name="sql">Sql语句</param>
        /// <param name="sqlParameter">Sql参数</param>
        /// <returns>返回受影响行数</returns>
        public static int ExecNonQuery(string sql, SqlParameter[] sqlParameter =null)
        {
            int num = 0;
            try
            {
                using (SqlConnection sqlConn = new SqlConnection(connStr))
                {
                    sqlConn.Open();
                    if (sqlConn.State == ConnectionState.Open)
                    {
                        using (SqlCommand cmd = new SqlCommand(sql, sqlConn))
                        {
                            if (sqlParameter != null && sqlParameter.Length > 0)
                                cmd.Parameters.AddRange(sqlParameter);
                            num = cmd.ExecuteNonQuery();
                        }
                    }
                }
                return num;
            }
            catch
            {
                return -1;
            }

        }
        /// <summary>
        /// 返回第一行第一列内容
        /// </summary>
        /// <param name="sql"></param>
        /// <param name="sqlParameters"></param>
        /// <returns></returns>
        public static string ExecScalar(string sql, SqlParameter[] sqlParameter = null)
        {
            string value = "";
            using (SqlConnection sqlConn = new SqlConnection(connStr))
            {
                sqlConn.Open();
                if (sqlConn.State == ConnectionState.Open)
                {
                    using (SqlCommand cmd = new SqlCommand(sql, sqlConn))
                    {
                        if (sqlParameter != null && sqlParameter.Length > 0)
                            cmd.Parameters.AddRange(sqlParameter);
                        value = cmd.ExecuteScalar().ToString();
                    }
                }
            }
            return value;
        }
    }
}

App.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
    <startup> 
        <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.7.2" />
    </startup>
  <connectionStrings>
    <add name="Demo" connectionString="Data Source=127.0.0.1;Initial Catalog=AdventureWorks;Persist Security Info=True;User ID=sa;Password=Sa123"/>
  </connectionStrings>
</configuration>