private static ParsedLike Parse(String inValue)
{
ParsedLike myParse = new ParsedLike();
String work = inValue;
Int32 loc;
if (!work.StartsWith("%"))
{
work = work.TrimStart('%');
loc = work.IndexOf("%");
myParse.startwith = work.Substring(0, loc);
work = work.Substring(loc + 1);
}
if (!work.EndsWith("%"))
{
loc = work.LastIndexOf('%');
myParse.endwith = work.Substring(loc + 1);
if (loc == -1)
{
work = String.Empty;
}
else
{
work = work.Substring(0, loc);
}
}
myParse.contains = work.Split(new[] { '%' }, StringSplitOptions.RemoveEmptyEntries);
return(myParse);
}
public static Expression <Func <T, Boolean> > BuildLikeExpression <T>(Expression <Func <T, String> > valueSelector, String value)
{
if (valueSelector == null)
{
throw new ArgumentNullException("valueSelector");
}
value = value.Replace("*", "%"); // this allows us to use '%' or '*' for our wildcard
if (value.Trim('%').Contains("%"))
{
Expression myBody = null;
ParsedLike myParse = Parse(value);
Type stringType = typeof(String);
if (myParse.startwith != null)
{
myBody = Expression.Call(valueSelector.Body, stringType.GetMethod("StartsWith", new Type[] { stringType }), Expression.Constant(myParse.startwith));
}
foreach (String contains in myParse.contains)
{
if (myBody == null)
{
myBody = Expression.Call(valueSelector.Body, stringType.GetMethod("Contains", new Type[] { stringType }), Expression.Constant(contains));
}
else
{
Expression myInner = Expression.Call(valueSelector.Body, stringType.GetMethod("Contains", new Type[] { stringType }), Expression.Constant(contains));
myBody = Expression.And(myBody, myInner);
}
}
if (myParse.endwith != null)
{
if (myBody == null)
{
myBody = Expression.Call(valueSelector.Body, stringType.GetMethod("EndsWith", new Type[] { stringType }), Expression.Constant(myParse.endwith));
}
else
{
Expression myInner = Expression.Call(valueSelector.Body, stringType.GetMethod("EndsWith", new Type[] { stringType }), Expression.Constant(myParse.endwith));
myBody = Expression.And(myBody, myInner);
}
}
return(Expression.Lambda <Func <T, Boolean> >(myBody, valueSelector.Parameters.Single()));
}
else
{
Expression myBody = Expression.Call(valueSelector.Body, GetLikeMethod(value), Expression.Constant(value.Trim('%')));
return(Expression.Lambda <Func <T, Boolean> >(myBody, valueSelector.Parameters.Single()));
}
}
