Parse an Expression into a SQL Where

gistfile1.cs

private string parsePredicateExpression(Expression body)
{
    BinaryExpression binary = (BinaryExpression)body; // cast
    string separator = body.NodeType == ExpressionType.OrElse ? " OR " : " AND ";

    if (body.NodeType == ExpressionType.AndAlso || body.NodeType == ExpressionType.OrElse)
    {   // If we are working with several ANDs or ORs
        return "(" + parsePredicateExpression(binary.Left) + separator + parsePredicateExpression(binary.Right) + ")";
    }
    else
    {
        MemberExpression member = (MemberExpression)binary.Left;
        string output = member.Member.Name;

        switch (body.NodeType)
        {   // Given the node type of the expression, we set the correct string, normally it's equal (x.Id == 1)
            default:
            case ExpressionType.Equal:
                output += " = ";
                break;
            case ExpressionType.NotEqual:
                output += " <> ";
                break;
            case ExpressionType.GreaterThan:
                output += " > ";
                break;
            case ExpressionType.GreaterThanOrEqual:
                output += " >= ";
                break;
            case ExpressionType.LessThan:
                output += " < ";
                break;
            case ExpressionType.LessThanOrEqual:
                output += " <= ";
                break;
        }

        object val = null;

        if (binary.Right.NodeType == ExpressionType.MemberAccess)
        {
            var exp = (MemberExpression)binary.Right;
            val = GetValue(exp);
        }
        else
        {
            ConstantExpression constant = (ConstantExpression)binary.Right;
            val = constant.Value;
        }

        if (val is int) { output += val; }
        else { output += "\"" + val + "\""; }

        return output;
    }
}

private object GetValue(MemberExpression member)
{
    var objectMember = Expression.Convert(member, typeof(object));
    var getterLambda = Expression.Lambda>(objectMember);
    var getter = getterLambda.Compile();
    return getter();
}