c#_执行数据库，增删改查

增

public static int Insert(string Conn,string SQL)
{
    int result = 0;
    using (SqlConnection cn = new())
    {
        //数据库连接字符串
        cn.ConnectionString = Conn;
        //打开字符串
        cn.Open();
        
        //声明对象
        using (SqlCommand cmd = new SqlCommand(SQL, cn))
        {
            result = cmd.ExecuteNonQuery();
        }
    }
    return result;
}

删

 public static int Delete(string Conn,string SQL)
 {
     int result = 0;
     using (SqlConnection cn = new())
     {
         //数据库连接字符串
         cn.ConnectionString = Conn;
          //打开字符串
         cn.Open();
         
         //声明对象
         using (SqlCommand cmd = new SqlCommand())
         {
             cmd.Connection = cn;
             //删除table中id的这一行
             cmd.CommandText = String.Format("delete from table where id=@id"); 
             //给参数赋值
             cmd.Parameters.Add("@id",SqlDbType.Int).Value= result;
             result = cmd.ExecuteNonQuery();
             result = cmd.ExecuteNonQuery();
         }
     }
     return result;
 }

改

public static int Update(string Conn,string SQL)
{
    int result = 0;
    using (SqlConnection cn = new())
    {
        cn.ConnectionString = Conn;
        cn.Open();
        using (SqlCommand cmd = new SqlCommand(SQL, cn))
        {
            result = cmd.ExecuteNonQuery();
        }
    }
    return result;
}

查

 public static DataTable GetDaTable(string Conn,string SQL, CommandType type = CommandType.Text, params SqlParameter[] SQLParams)
 {
     using (SqlConnection conn = new(Conn))
     {
         conn.Open();
         SqlCommand dbCommand = new SqlCommand();
         dbCommand.Connection = conn;

         dbCommand.CommandText = SQL;
         dbCommand.CommandType = type;
         if (SQLParams != null)
         {
             dbCommand.Parameters.AddRange(SQLParams);
         }

         DataTable dataTable = new DataTable();
         try
         {
             using (DbDataReader reader = dbCommand.ExecuteReader())
             {
                 dataTable.Load(reader);
                 return dataTable;
             }
         }
         finally
         {
             conn.Close();
             ((IDisposable)dataTable)?.Dispose();
         }
     }
 }
       

public static string GetStringValue(string Conn, string SQL)
{
    SqlConnection conn = new SqlConnection(Conn);
    conn.Open();
    string strField;
    DataTable dt = new();
    SqlDataAdapter da = new(SQL, Conn);
    da.Fill(dt);
    conn.Close();
    if (dt.Rows.Count > 0)
    {
        strField = dt.Rows[0][0].ToString().Trim();
    }
    else
    {
        strField = string.Empty;
    }
    return strField;
}