System.Web.UI.WebControls.Unit 的行为
Posted
技术标签:
【中文标题】System.Web.UI.WebControls.Unit 的行为【英文标题】：Behaviour of System.Web.UI.WebControls.Unit 【发布时间】：2017-09-18 13:38:18 【问题描述】：我有一个asp:TextBox，我可以通过以下方式设置width：
<asp:TextBox runat="server" ID="TextBox1" Width="100"></asp:TextBox>
或
<asp:TextBox runat="server" ID="TextBox1" Width="100%"></asp:TextBox>
在 Codebehind 中我只能设置
TextBox1.Width = 100; // remember, Width is type of Unit, not int
不可能是这样的：
TextBox1.Width = "100%";
我的期望
TextBox1.Width = new Unit.. ;
问题：为什么nUnit 会这样？为什么int 可能但string 不可能，为什么不期望Unit 的新对象？
【问题讨论】：
【参考方案1】：你可以这样设置百分比。
TextBox1.Width = System.Web.UI.WebControls.Unit.Percentage(90);
【讨论】：
【参考方案2】：TextBox 是一个WebControl，其中 Width 是一个虚拟属性，定义为：
[DefaultValue(typeof(Unit), "")]
[WebCategory("Layout")]
[WebSysDescription("WebControl_Width")]
public virtual Unit Width
get
if (!this.ControlStyleCreated)
return Unit.Empty;
return this.ControlStyle.Width;
set
this.ControlStyle.Width = value;
Unit 是一个结构（这是您问题的答案）：
[Serializable]
[TypeConverter(typeof(UnitConverter))]
public struct Unit
internal const int MaxValue = 32767;
internal const int MinValue = -32768;
public readonly static Unit Empty;
private readonly UnitType type;
private readonly double @value;
public bool IsEmpty
get
return (int)this.type == 0;
public UnitType Type
get
if (this.IsEmpty)
return UnitType.Pixel;
return this.type;
public double Value
get
return this.@value;
static Unit()
Unit.Empty = new Unit();
public Unit(int value)
if (value < -32768 || value > 32767)
throw new ArgumentOutOfRangeException("value");
this.@value = (double)value;
this.type = UnitType.Pixel;
public Unit(double value)
if (value < -32768 || value > 32767)
throw new ArgumentOutOfRangeException("value");
this.@value = (double)((int)value);
this.type = UnitType.Pixel;
public Unit(double value, UnitType type)
if (value < -32768 || value > 32767)
throw new ArgumentOutOfRangeException("value");
if (type != UnitType.Pixel)
this.@value = value;
else
this.@value = (double)((int)value);
this.type = type;
public Unit(string value) : this(value, CultureInfo.CurrentCulture, UnitType.Pixel)
public Unit(string value, CultureInfo culture) : this(value, culture, UnitType.Pixel)
internal Unit(string value, CultureInfo culture, UnitType defaultType)
if (string.IsNullOrEmpty(value))
this.@value = 0;
this.type = (UnitType)0;
return;
if (culture == null)
culture = CultureInfo.CurrentCulture;
string lower = value.Trim().ToLower(CultureInfo.InvariantCulture);
int length = lower.Length;
int num = -1;
for (int i = 0; i < length; i++)
char chr = lower[i];
if ((chr < '0' || chr > '9') && chr != '-' && chr != '.' && chr != ',')
break;
num = i;
if (num == -1)
object[] objArray = new object[] value ;
throw new FormatException(SR.GetString("UnitParseNoDigits", objArray));
if (num >= length - 1)
this.type = defaultType;
else
this.type = Unit.GetTypeFromString(lower.Substring(num + 1).Trim());
string str = lower.Substring(0, num + 1);
try
TypeConverter singleConverter = new SingleConverter();
this.@value = (double)((float)singleConverter.ConvertFromString(null, culture, str));
if (this.type == UnitType.Pixel)
this.@value = (double)((int)this.@value);
catch
object[] objArray1 = new object[] value, str, this.type.ToString("G") ;
throw new FormatException(SR.GetString("UnitParseNumericPart", objArray1));
if (this.@value < -32768 || this.@value > 32767)
throw new ArgumentOutOfRangeException("value");
public override bool Equals(object obj)
if (obj == null || !(obj is Unit))
return false;
Unit unit = (Unit)obj;
if (unit.type == this.type && unit.@value == this.@value)
return true;
return false;
public override int GetHashCode()
return HashCodeCombiner.CombineHashCodes(this.type.GetHashCode(), this.@value.GetHashCode());
private static string GetStringFromType(UnitType type)
switch (type)
case UnitType.Pixel:
return "px";
case UnitType.Point:
return "pt";
case UnitType.Pica:
return "pc";
case UnitType.Inch:
return "in";
case UnitType.Mm:
return "mm";
case UnitType.Cm:
return "cm";
case UnitType.Percentage:
return "%";
case UnitType.Em:
return "em";
case UnitType.Ex:
return "ex";
return string.Empty;
private static UnitType GetTypeFromString(string value)
if (string.IsNullOrEmpty(value))
return UnitType.Pixel;
if (value.Equals("px"))
return UnitType.Pixel;
if (value.Equals("pt"))
return UnitType.Point;
if (value.Equals("%"))
return UnitType.Percentage;
if (value.Equals("pc"))
return UnitType.Pica;
if (value.Equals("in"))
return UnitType.Inch;
if (value.Equals("mm"))
return UnitType.Mm;
if (value.Equals("cm"))
return UnitType.Cm;
if (value.Equals("em"))
return UnitType.Em;
if (!value.Equals("ex"))
throw new ArgumentOutOfRangeException("value");
return UnitType.Ex;
public static bool operator ==(Unit left, Unit right)
if (left.type != right.type)
return false;
return left.@value == right.@value;
public static implicit operator Unit(int n)
return Unit.Pixel(n);
public static bool operator !=(Unit left, Unit right)
if (left.type != right.type)
return true;
return left.@value != right.@value;
public static Unit Parse(string s)
return new Unit(s, CultureInfo.CurrentCulture);
public static Unit Parse(string s, CultureInfo culture)
return new Unit(s, culture);
public static Unit Percentage(double n)
return new Unit(n, UnitType.Percentage);
public static Unit Pixel(int n)
return new Unit(n);
public static Unit Point(int n)
return new Unit((double)n, UnitType.Point);
public override string ToString()
return this.ToString((IFormatProvider)CultureInfo.CurrentCulture);
public string ToString(CultureInfo culture)
return this.ToString((IFormatProvider)culture);
public string ToString(IFormatProvider formatProvider)
string str;
if (this.IsEmpty)
return string.Empty;
str = (this.type != UnitType.Pixel ? ((float)this.@value).ToString(formatProvider) : ((int)this.@value).ToString(formatProvider));
return string.Concat(str, Unit.GetStringFromType(this.type));
它定义了一个UnitConverter:
public class UnitConverter : TypeConverter
public UnitConverter()
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
if (sourceType == typeof(string))
return true;
return base.CanConvertFrom(context, sourceType);
public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType)
if (destinationType == typeof(string) || destinationType == typeof(InstanceDescriptor))
return true;
return base.CanConvertTo(context, destinationType);
public override object ConvertFrom(ITypeDescriptorContext context, CultureInfo culture, object value)
if (value == null)
return null;
string str = value as string;
if (str == null)
return base.ConvertFrom(context, culture, value);
string str1 = str.Trim();
if (str1.Length == 0)
return Unit.Empty;
if (culture != null)
return Unit.Parse(str1, culture);
return Unit.Parse(str1, CultureInfo.CurrentCulture);
public override object ConvertTo(ITypeDescriptorContext context, CultureInfo culture, object value, Type destinationType)
if (destinationType == typeof(string))
if (value == null || ((Unit)value).IsEmpty)
return string.Empty;
return ((Unit)value).ToString(culture);
if (destinationType != typeof(InstanceDescriptor) || value == null)
return base.ConvertTo(context, culture, value, destinationType);
Unit unit = (Unit)value;
MemberInfo constructor = null;
object[] objArray = null;
if (!unit.IsEmpty)
Type type = typeof(Unit);
Type[] typeArray = new Type[] typeof(double), typeof(UnitType) ;
constructor = type.GetConstructor(typeArray);
object[] objArray1 = new object[] unit.Value, unit.Type ;
objArray = objArray1;
else
constructor = typeof(Unit).GetField("Empty");
if (constructor == null)
return null;
return new InstanceDescriptor(constructor, objArray);
在此代码中，您可以找到问题的答案。
【讨论】：
【参考方案3】：Unit 是一个结构体，如果你的意思是Unit
试试 myUnit.Value。它将获得所指出的值。 您可以使用constructor 然后public Unit(int value) 转换回来。
我认为这应该会有所帮助。
【讨论】：
以上是关于System.Web.UI.WebControls.Unit 的行为的主要内容，如果未能解决你的问题，请参考以下文章
System.Web.UI.WebControls.Unit 的行为
System.Web.UI.WebControls.Image 不包含保存的定义？保存图像
获取 ASP.NET System.Web.UI.WebControls.PlaceHolder 的内容
将 varchar 值“System.Web.UI.WebControls.TextBox”转换为数据类型 int 时转换失败。
System.Web.UI.WebControls.TextBox”不包含“text”的定义，并且找不到可接受类型为“System.Web.UI.Web
仅对具有 DataBinding 事件的对象提供数据绑定表达式支持。System.Web.UI.WebControls.HyperLinkField 没