Databases
StackOverflow2013
Postsdbo
POPassing int list as a parameter to a web user control
Body
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POPassing int list as a parameter to a web user control
    text
    copied!<p>I want to pass an int list (List) as a declarative property to a web user control like this:</p> <pre><code>&lt;UC:MyControl runat="server" ModuleIds="1,2,3" /&gt; </code></pre> <p>I created a TypeConverter to do this:</p> <pre><code>public class IntListConverter : System.ComponentModel.TypeConverter { public override bool CanConvertFrom( System.ComponentModel.ITypeDescriptorContext context, Type sourceType) { if (sourceType == typeof(string)) return true; return base.CanConvertFrom(context, sourceType); } public override object ConvertFrom( System.ComponentModel.ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value) { if (value is string) { string[] v = ((string)value).Split( new char[] { ',' }, StringSplitOptions.RemoveEmptyEntries); List&lt;int&gt; list = new List&lt;int&gt;(); foreach (string s in vals) { list.Add(Convert.ToInt32(s)); } return list } return base.ConvertFrom(context, culture, value); } public override bool CanConvertTo(ITypeDescriptorContext context, Type destinationType) { if (destinationType == typeof(InstanceDescriptor)) return true; return base.CanConvertTo(context, destinationType); } public override object ConvertTo(ITypeDescriptorContext context, System.Globalization.CultureInfo culture, object value, Type destinationType) { if (destinationType == typeof(InstanceDescriptor) &amp;&amp; value is List&lt;int&gt;) { List&lt;int&gt; list = (List&lt;int&gt;)value; ConstructorInfo construcor = typeof(List&lt;int&gt;).GetConstructor(new Type[] { typeof(IEnumerable&lt;int&gt;) }); InstanceDescriptor id = new InstanceDescriptor(construcor, new object[] { list.ToArray() }); return id; } return base.ConvertTo(context, culture, value, destinationType); } } </code></pre> <p>And then added the attribute to my property:</p> <pre><code>[TypeConverter(typeof(IntListConverter))] public List&lt;int&gt; ModuleIds { get { ... }; set { ... }; } </code></pre> <p>But I get this error at runtime:</p> <p><code>Unable to generate code for a value of type 'System.Collections.Generic.List'1[[System.Int32, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]'. This error occurred while trying to generate the property value for ModuleIds.</code></p> <p>My question is similar to one found <a href="https://stackoverflow.com/questions/116797/passing-int-array-as-parameter-in-web-user-control">here</a>, but the solution does not solve my problem:</p> <p><strong>Update:</strong> I found a page which solved the first problem. I updated the code above to show my fixes. The added code is the <code>CanConvertTo</code> and <code>ConvertTo</code> methods. Now I get a different error.:</p> <p><code>Object reference not set to an instance of an object.</code></p> <p>This error seems to be indirectly caused by something in the <code>ConvertTo</code> method.</p>
 

Querying!

 
Guidance
An individual column

Larger individual text columns get their own page to allow for proper reading.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload