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POC# Generics and Casting Issue
 

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  1. POC# Generics and Casting Issue
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    <p>I am having trouble casting an object to a generic IList. I have a group of in statements to try to work around this, but there has to be a better way to do this.</p> <p>This is my current method:</p> <pre><code>string values; if (colFilter.Value is IList&lt;int&gt;) { values = BuildClause((IList&lt;int&gt;)colFilter.Value, prefix); } else if (colFilter.Value is IList&lt;string&gt;) { values = BuildClause((IList&lt;string&gt;)colFilter.Value, prefix); } else if (colFilter.Value is IList&lt;DateTime&gt;) { values = BuildClause((IList&lt;DateTime&gt;)colFilter.Value, prefix); } else if (...) //etc. </code></pre> <p>What I want to do is this: </p> <pre><code>values = BuildClause((IList&lt;colFilter.ColumnType&gt;)colFilter.Value, prefix); </code></pre> <p>or</p> <pre><code>values = BuildClause((IList&lt;typeof(colFilter.ColumnType)&gt;)colFilter.Value, prefix); </code></pre> <p>or</p> <pre><code>values = BuildClause((IList&lt;colFilter.ColumnType.GetType()&gt;)colFilter.Value, prefix); </code></pre> <p>Each of these produces this compiler error: The type or namespace name 'colFilter' could not be found (are you missing a using directive or an assembly reference?)</p> <p>In my example, colFilter.ColumnType is int, string, datetime, etc. I am not sure why this does not work. </p> <p>Any ideas?</p> <p><strong>EDIT: This is C#2.0</strong></p> <p><strong>EDIT #2</strong></p> <p>Here is the BuildClause method (I have overloads for each type):</p> <pre><code>private static string BuildClause(IList&lt;int&gt; inClause, string strPrefix) { return BuildClause(inClause, strPrefix, false); } private static string BuildClause(IList&lt;String&gt; inClause, string strPrefix) { return BuildClause(inClause, strPrefix, true); } private static string BuildClause(IList&lt;DateTime&gt; inClause, string strPrefix) { return BuildClause(inClause, strPrefix, true); } //.. etc for all types private static string BuildClause&lt;T&gt;(IList&lt;T&gt; inClause, string strPrefix, bool addSingleQuotes) { StringBuilder sb = new StringBuilder(); //Check to make sure inclause has objects if (inClause.Count &gt; 0) { sb.Append(strPrefix); sb.Append(" IN("); for (int i = 0; i &lt; inClause.Count; i++) { if (addSingleQuotes) { sb.AppendFormat("'{0}'", inClause[i].ToString().Replace("'", "''")); } else { sb.Append(inClause[i].ToString()); } if (i != inClause.Count - 1) { sb.Append(","); } } sb.Append(") "); } else { throw new Exception("Item count for In() Clause must be greater than 0."); } return sb.ToString(); } </code></pre>
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