public static Expression GetExpression <T>(ParameterExpression param, ExpressionFilter filter)
{
MemberExpression member = GetEndpointProperty(param, filter);
ConstantExpression constant = Expression.Constant(filter.Value, member.Type);
switch (filter.ComparisonType)
{
case ComparisonType.Equal:
return(Expression.Equal(member, constant));
case ComparisonType.GreaterThan:
return(Expression.GreaterThan(member, constant));
case ComparisonType.GreaterThanOrEqual:
return(Expression.GreaterThanOrEqual(member, constant));
case ComparisonType.LessThan:
return(Expression.LessThan(member, constant));
case ComparisonType.LessThanOrEqual:
return(Expression.LessThanOrEqual(member, constant));
case ComparisonType.NotEqual:
return(Expression.NotEqual(member, constant));
case ComparisonType.Contains:
return(Expression.Call(member, ContainsMethod, constant));
case ComparisonType.StartsWith:
return(Expression.Call(member, StartsWithMethod, constant));
case ComparisonType.EndsWith:
return(Expression.Call(member, EndsWithMethod, constant));
default:
return(null);
}
}
private static MemberExpression GetEndpointProperty(ParameterExpression param, ExpressionFilter filter)
{
var properties = filter.PropertyName.Split('.');
if (properties.Length == 0)
{
return(null);
}
var expression = Expression.Property(param, properties[0]);
for (var i = 1; i < properties.Length; i++)
{
expression = Expression.Property(expression, properties[i]);
}
return(expression);
}