/// <summary>
/// 使用提供的条件查询数据库（表由entityType指定），返回满足条件的记录（分页）
/// </summary>
/// <typeparam name="T">要查询的实体类型，标记了DbTable和DbField特性的类，并且具有空白构造函数</typeparam>
/// <param name="connector"></param>
/// <param name="criteria">查询条件字典，键是PropertyName，条件仅支持=比较，条件间仅支持AND运算</param>
/// <param name="pageIndex">从0开始的返回页索引</param>
/// <param name="pageSize">每页几行记录</param>
/// <param name="sortProperty">用于排序的PropertyName(如为空则使用关键字)</param>
/// <param name="descending">是否倒序排列</param>
/// <param name="total">符合条件的记录总数</param>
/// <returns></returns>
public static async Task <PagedQuery <T> > SearchEntities <T>(DbConnector connector, Dictionary <string, object> criteria,
int pageIndex, int pageSize, string sortProperty, bool descending) where T : new()
{
Type entityType = typeof(T);
if (!(DbTableAttribute.GetCustomAttribute(entityType, typeof(DbTableAttribute)) is DbTableAttribute tableAttr))
{
throw new Exception("类型" + entityType.FullName + "没有标记DbTableAttribute特性");
}
string selectClause = "SELECT * ";
string fromClause = "FROM " + tableAttr.TableName;
string orderBy;
#region 正确处理orderBy
DbFieldAttribute sortFieldAttr = null;
if (string.IsNullOrWhiteSpace(sortProperty))
{
//如果没有传递sortProperty参数, 则使用PrimaryKey
foreach (PropertyInfo property in entityType.GetProperties())
{
DbFieldAttribute fldAttr = DbFieldAttribute.GetCustomAttribute(property, typeof(DbFieldAttribute)) as DbFieldAttribute;
if (fldAttr != null && fldAttr.IsPrimaryKey)
{
sortFieldAttr = fldAttr;
break;
}
}
}
else
{
PropertyInfo property = entityType.GetProperty(sortProperty);
if (property == null)
{
throw new Exception(string.Format("类型{0}中没有找到{1}属性用于排序", entityType.FullName, sortProperty));
}
sortFieldAttr = DbFieldAttribute.GetCustomAttribute(property, typeof(DbFieldAttribute)) as DbFieldAttribute;
}
if (sortFieldAttr == null)
{
throw new Exception("类型" + entityType.FullName + "没有标记IsPrimaryKey=true的DbField特性");
}
if (descending)
{
orderBy = sortFieldAttr.FieldName + " DESC";
}
else
{
orderBy = sortFieldAttr.FieldName;
}
#endregion
StringBuilder whereBuilder = new StringBuilder();
List <SqlParameter> sqlParameters = new List <SqlParameter>();
if (criteria != null)
{
foreach (string conditionName in criteria.Keys)
{
if (criteria[conditionName] == null || criteria[conditionName].ToString().Length == 0)
{
continue;
}
PropertyInfo conditionProperty = entityType.GetProperty(conditionName);
if (conditionProperty == null)
{
throw new Exception(string.Format("类型{0}中没有找到{1}属性用于查询条件", entityType.FullName, conditionName));
}
DbFieldAttribute conditionAttr = DbFieldAttribute.GetCustomAttribute(conditionProperty, typeof(DbFieldAttribute)) as DbFieldAttribute;
if (conditionAttr == null)
{
throw new Exception(string.Format("类型{0}的{1}属性没有标记DbFieldAttribute特性, 无法用于数据库查询",
entityType.FullName, conditionName));
}
SqlParameter parameter = GenerateSqlParameter(conditionAttr, conditionProperty.PropertyType, criteria[conditionName]);
sqlParameters.Add(parameter);
whereBuilder.AppendFormat("[{0}]=@{0} ", conditionAttr.FieldName);
whereBuilder.Append("AND ");
}
}
if (whereBuilder.Length > 0)
{
whereBuilder.Remove(whereBuilder.Length - 4, 4);
}
string sql = BuildPagedSelectSql(selectClause, fromClause, whereBuilder.ToString(), orderBy, pageIndex, pageSize);
DataSet ds = await connector.ExecuteSqlQuerySet(sql, sqlParameters.ToArray());
PagedQuery <T> result = new PagedQuery <T>();
if (ds != null && ds.Tables.Count == 2)
{
result.Total = (int)ds.Tables[0].Rows[0][0];
ds.Tables[1].TableName = "result";
result.Records = await Task.Run(() => ValueHelper.WrapEntities <T>(ds.Tables[1]));
}
else
{
result.Total = 0;
result.Records = new T[0];
}
ds.Dispose();
return(result);
}
/// <summary>
/// 分页读取数据库中全部实体，不带查询条件
/// </summary>
/// <typeparam name="T">实体类</typeparam>
/// <param name="connector">数据源</param>
/// <param name="pageIndex">读取的页（从0开始）</param>
/// <param name="pageSize">每页包含记录条数</param>
/// <param name="sortProperty">排序方法</param>
/// <returns></returns>
public static async Task <PagedQuery <T> > QueryPagedEntity <T>(DbConnector connector, int pageIndex, int pageSize,
string sortProperty, bool descending) where T : new() =>
await SearchEntities <T>(connector, null, pageIndex, pageSize, sortProperty, descending);
