MIN and MAX value by string in Entity Framework
<p>I have database table. The ORM for it is:</p>

<pre><code>public long Id { get; set; }
public System.Guid AttrId { get; set; }
public System.Guid ProdId { get; set; }
public string Value { get; set; }

public virtual Attributes Attributes { get; set; }
public virtual Products Products { get; set; }
</code></pre>

<p>As you can see value is a string type. I'm trying to get min and max values by this field (some values represented as double). So here is my method for this:</p>

<pre><code>public double[] GetMaxMinVals(Guid attrId)
{
    double[] res = new double[2];
    using(entityContext = new SiteDBEntities())
    {
        res[0] = entityContext.ProductAttributes.Where(x=&gt;x.AttrId == attrId)
            .Min(x =&gt; Convert.ToDouble(x.Value));
        res[1] = entityContext.ProductAttributes.Where(x =&gt; x.AttrId == attrId)
            .Max(x =&gt; Convert.ToDouble(x.Value));
    }

    return res;
}
</code></pre>

<p>But I getting exception:</p>

<blockquote>
  <p>LINQ to Entities does not recognize the method 'Double ToDouble(System.String)' method, and this method cannot be translated into a store expression.</p>
</blockquote>

<p>So how can I search for a string value like a decimal?</p>