MySQL通过实例化对象参数查询实例讲解

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  public static string QueryByEntity<T>(T t) where T : new()  {  string resultstr = string.Empty;    MySqlDataReader reader = null;  try    {      Type type = typeof(T);      PropertyInfo[] properties = type.GetProperties();    string select = string.Format("Select * from {0} {1}", type.Name, "{0}");    string where = string.Empty;    foreach (PropertyInfo property in properties)      {      var value = t.GetPropertyValue<T>(property);      if (value != null && !value.Equals(property.GetDefaultValue()))        {        if (string.IsNullOrEmpty(where))          {          where = string.Format(" where {0}='{1}' ", property.Name, value);          }        else          {          where = string.Format(" {0} and {1} = '{2}' ", where, property.Name, value);          }        }      }    select = string.Format(select, where);         MySqlConnection connection = OpenConnection();    if (connection == null)      return resultstr;      MySqlCommand _sqlCom = new MySqlCommand(select, connection);      reader = _sqlCom.ExecuteReader();      List<T> tList = new List<T>();    while (reader.Read())      {        T t1 = new T();      foreach (PropertyInfo property in properties)        {        if (!string.IsNullOrEmpty(reader[property.Name].ToString()))          {            property.SetMethod.Invoke(t1, new object[] { reader[property.Name] });          }        }        tList.Add(t1);      }      resultstr = JsonConvert.SerializeObject(tList);    }  catch (Exception ex)    {      Logging.Error(string.Format("查询数据库失败，{0}", ex.Message));    }  finally    {    if (reader != null)      {        reader.Close();        reader.Dispose();      }    }  return resultstr;  }internal static class ObjectExtend  {  public static object GetPropertyValue<T>(this object obj, PropertyInfo property)    {      Type type = typeof(T);      PropertyInfo propertyInfo = type.GetProperty(property.Name);    if (propertyInfo != null)      {      return propertyInfo.GetMethod.Invoke(obj, null);      }    return null;    }  public static object GetDefaultValue(this PropertyInfo property)    {    return property.PropertyType.IsValueType ? Activator.CreateInstance(property.PropertyType) : null;    }  }

通过实例化参数，对属性赋值，将对象作为参数传入，反射获取对象名称，列名，列值。要求对象名与表名一致，属性与列名一致。