一行代码搞定你的QueryString！（原创）

清疚 2021-12-21 03:29 250阅读 0赞

Web开发做得多了，总觉得是体力活，于是搞些代码让自己脱离无聊的Coding吧（是脱离“无聊的”Coding，不是脱离无聊的“Coding”）。

# 初级阶段 #

为每个QueryString写转换的代码，针对不同的类型，进行转换和错误处理。

# 中级阶段 #

写了一个函数，专门做转换（1.1里写的）：

///  <summary>   
 ///  Convert query string to parameter.  
 ///  </summary>   
 ///  <param name="name"> Name of query string </param>   
 ///  <param name="defaultValue"> Default value of query string </param>   
 ///  <param name="isRequired"> If the query string is required </param>   
  private  object  ConvertParameter( string  name,  object  defaultValue,  bool  isRequired)

# 高级阶段 #

昨天写的，第一次发文，大家拍砖吧：

主要是用了Attribute和反射的思想，首先给变量设置HttpQueryString的属性，绑定上相应的QueryString，然后由Page基类来读取相应的QueryString信息。  
  
属性这么写（HttpQueryStringAttribute.cs）：

using  System;  
  
 namespace  GooKuu.Framework.Web  
\{  
  
 ///  <summary>   
 ///  Specifies a field for a query string.  
 ///  </summary>   
  \[AttributeUsage(AttributeTargets.Field)\]  
 public  sealed  class  HttpQueryStringAttribute : Attribute  
\{  
 private  string  \_name;  
 private  object  \_defaultValue;  
 private  bool  \_isRequired;  
  
 ///  <summary>   
 ///  Constructor. The query string must be provided.  
 ///  </summary>   
 ///  <param name="name"> Name of the query string </param>   
  public  HttpQueryStringAttribute( string  name)  
\{  
\_name  =  name;  
\_defaultValue  =  null ;  
\_isRequired  =  true ;  
\}  
  
 ///  <summary>   
 ///  Constructor. If the query string is not be provided, using the default value.  
 ///  </summary>   
 ///  <param name="name"> Name of the query string </param>   
 ///  <param name="defaultValue"> Default value of the query string which is not provided </param>   
  public  HttpQueryStringAttribute( string  name,  object  defaultValue)  
\{  
\_name  =  name;  
\_defaultValue  =  defaultValue;  
\_isRequired  =  false ;  
\}  
  
 ///  <summary>   
 ///  Name of the query string.  
 ///  </summary>   
  public  string  Name  
\{  
 get  \{  return  \_name; \}  
\}  
  
 ///  <summary>   
 ///  Default value of the query string which is not provided.  
 ///  </summary>   
  public  object  DefaultValue  
\{  
 get  \{  return  \_defaultValue; \}  
\}  
  
 ///  <summary>   
 ///  Indicates if the query string must be provided.  
 ///  </summary>   
  public  bool  IsRequired  
\{  
 get  \{  return  \_isRequired; \}  
\}  
\}  
\}

页面基类是这样的（PageBase.cs）：

using  System;  
 using  System.Reflection;  
 using  System.Web;  
 using  System.Web.UI;  
  
 namespace  GooKuu.Framework.Web  
\{  
 ///  <summary>   
 ///  Base class of all pages.  
 ///  </summary>   
  public  class  PageBase : Page  
\{  
 ///  <summary>   
 ///  Override OnLoad method of base class.  
 ///  </summary>   
 ///  <param name="e"></param>   
  protected  override  void  OnLoad(System.EventArgs e)  
\{  
ParameterInitialize();  
 base .OnLoad(e);  
\}  
  
 ///  <summary>   
 ///  Initialize parameters according to query strings.  
 ///  </summary>   
  private  void  ParameterInitialize()  
\{  
 //  Get Type of current page class.   
  Type type  =  this .GetType();  
  
 //  Get all fields of current page class.   
  FieldInfo\[\] fields  =  type.GetFields();  
  
 foreach  (FieldInfo field  in  fields)  
\{  
 //  Get HttpQueryStringAttribute of current field.   
  HttpQueryStringAttribute attribute  =  (HttpQueryStringAttribute)Attribute.GetCustomAttribute(field,  typeof (HttpQueryStringAttribute));  
  
 //  If has HttpQueryStringAttribute, this field is for a query string.   
  if  (attribute  !=  null )  
\{  
SetField(field, attribute);  
\}  
\}  
\}  
  
 ///  <summary>   
 ///  Set field according to the HttpQueryStringAttribute.  
 ///  </summary>   
 ///  <param name="field"> The field will be set </param>   
 ///  <param name="attribute"> The attribute of current field </param>   
  private  void  SetField(FieldInfo field, HttpQueryStringAttribute attribute)  
\{  
 //  The query string must be provided.   
  if  (attribute.IsRequired)  
\{  
 if  (Request.QueryString\[attribute.Name\]  !=  null )  
\{  
SetFieldValue(field,  this , attribute.Name, field.FieldType);  
\}  
 else   
\{  
 throw  new  Exception( string .Format( " Query string \\ " \{  0 \}\\ "  is required " , attribute.Name),  new  NullReferenceException());  
\}  
\}  
 //  If the query string is not be provided, using the default value.   
  else   
\{  
 if  (attribute.DefaultValue  ==  null  ||  field.FieldType  ==  attribute.DefaultValue.GetType())  
\{  
 if  (Request.QueryString\[attribute.Name\]  ==  null  ||  Request.QueryString\[attribute.Name\]  ==  string .Empty)  
\{  
field.SetValue( this , attribute.DefaultValue);  
\}  
 else   
\{  
SetFieldValue(field,  this , attribute.Name, field.FieldType);  
\}  
\}  
 else   
\{  
 throw  new  Exception( string .Format( " Invalid default value of query string \\ " \{  0 \}\\ " (\{1\}) " , attribute.Name, field.Name),  new  NullReferenceException());  
\}  
\}  
\}  
  
 ///  <summary>   
 ///  Set the value of current field according to the query string.  
 ///  </summary>   
 ///  <param name="field"> The field will be set </param>   
 ///  <param name="obj"> The object whose field value will be set </param>   
 ///  <param name="name"> The name of query string </param>   
 ///  <param name="conversionType"> The type to be converted </param>   
  private  void  SetFieldValue(FieldInfo field,  object  obj,  string  name, Type conversionType)  
\{  
 try   
\{  
 //  Set field value.   
  field.SetValue(obj, Convert.ChangeType(Request.QueryString\[name\], conversionType));  
\}  
 catch  (Exception ex)  
\{  
 throw  new  Exception( string .Format( " The given value of query string \\ " \{  0 \}\\ "  can not be convert to \{1\} " , name, conversionType), ex);  
\}  
\}  
\}  
\}

在页面里，这样写就OK了（Default.aspx.cs）：

using  System;  
 using  System.Data;  
 using  System.Configuration;  
 using  System.Collections;  
 using  System.Web;  
 using  System.Web.Security;  
 using  System.Web.UI;  
 using  System.Web.UI.WebControls;  
 using  System.Web.UI.WebControls.WebParts;  
 using  System.Web.UI.HtmlControls;  
 using  GooKuu.Framework.Web;  
  
 public  partial  class  \_Default : PageBase  
\{  
  
 ///  <summary>   
 ///  Name 是Query String的名字，"Anonymous"是缺省值。  
 ///  如果没有提供这个Query String，就采用缺省值。  
 ///  </summary>   
  \[HttpQueryString( " Name " ,  " Anonymous " )\]  
 public  string  name;  
  
 ///  <summary>   
 ///  UserId 是Query String的名字，不提供缺省值。  
 ///  如果没有提供这个Query String或者提供的格式不正确导致转换失败，都会抛出异常。  
 ///  </summary>   
  \[HttpQueryString( " UserId " )\]  
 public  int  userId;  
  
 protected  void  Page\_Load( object  sender, EventArgs e)  
\{  
Response.Write( string .Format( " Name is \{0\}<br/> " , name));  
Response.Write( string .Format( " UserId is \{0\}<br/> " , userId));  
\}  
\}

转载于:https://www.cnblogs.com/arielyang/archive/2006/01/16/318044.html